diff --git a/Cargo.lock b/Cargo.lock
index 91b25c4949aa..ae6eaffe1089 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -128,7 +128,7 @@ checksum = "514de17de45fdb8dc022b1a7975556c53c86f9f0aa5f534b98977b171857c2c9"
 [[package]]
 name = "cairo-rs"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "bitflags 2.6.0",
  "cairo-sys-rs",
@@ -139,7 +139,7 @@ dependencies = [
 [[package]]
 name = "cairo-sys-rs"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "glib-sys",
  "libc",
@@ -391,7 +391,7 @@ dependencies = [
 [[package]]
 name = "gdk-pixbuf"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "gdk-pixbuf-sys",
  "gio",
@@ -402,7 +402,7 @@ dependencies = [
 [[package]]
 name = "gdk-pixbuf-sys"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "gio-sys",
  "glib-sys",
@@ -551,7 +551,7 @@ checksum = "40ecd4077b5ae9fd2e9e169b102c6c330d0605168eb0e8bf79952b256dbefffd"
 [[package]]
 name = "gio"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "futures-channel",
  "futures-core",
@@ -567,7 +567,7 @@ dependencies = [
 [[package]]
 name = "gio-sys"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "glib-sys",
  "gobject-sys",
@@ -616,7 +616,7 @@ dependencies = [
 [[package]]
 name = "glib"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "bitflags 2.6.0",
  "futures-channel",
@@ -636,7 +636,7 @@ dependencies = [
 [[package]]
 name = "glib-macros"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "heck",
  "proc-macro-crate",
@@ -648,7 +648,7 @@ dependencies = [
 [[package]]
 name = "glib-sys"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "libc",
  "system-deps",
@@ -688,7 +688,7 @@ dependencies = [
 [[package]]
 name = "gobject-sys"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "glib-sys",
  "libc",
@@ -698,7 +698,7 @@ dependencies = [
 [[package]]
 name = "graphene-rs"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "glib",
  "graphene-sys",
@@ -708,7 +708,7 @@ dependencies = [
 [[package]]
 name = "graphene-sys"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "glib-sys",
  "libc",
@@ -1171,7 +1171,7 @@ checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 [[package]]
 name = "pango"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "gio",
  "glib",
@@ -1182,7 +1182,7 @@ dependencies = [
 [[package]]
 name = "pango-sys"
 version = "0.21.0"
-source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#a1a0fdc1e02409a40fe706e18fea19abad6320fa"
+source = "git+https://github.com/gtk-rs/gtk-rs-core?branch=master#f69594c2f59643d60d1cf82081804b2a536f9f31"
 dependencies = [
  "glib-sys",
  "gobject-sys",
@@ -1716,9 +1716,9 @@ checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
 
 [[package]]
 name = "syn"
-version = "2.0.77"
+version = "2.0.79"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9f35bcdf61fd8e7be6caf75f429fdca8beb3ed76584befb503b1569faee373ed"
+checksum = "89132cd0bf050864e1d38dc3bbc07a0eb8e7530af26344d3d2bbbef83499f590"
 dependencies = [
  "proc-macro2",
  "quote",
diff --git a/examples/virtual_methods/base_button/mod.rs b/examples/virtual_methods/base_button/mod.rs
index af6e755a288b..a0139bcd5356 100644
--- a/examples/virtual_methods/base_button/mod.rs
+++ b/examples/virtual_methods/base_button/mod.rs
@@ -60,7 +60,7 @@ impl<O: IsA<BaseButton>> BaseButtonExt for O {}
 /// implement.
 ///
 /// See `derived_button/imp.rs` for how to override virtual methods.
-pub trait BaseButtonImpl: ButtonImpl {
+pub trait BaseButtonImpl: ButtonImpl + ObjectSubclass<Type: IsA<BaseButton>> {
     /// Default implementation of a virtual method.
     ///
     /// This always calls into the implementation of the parent class so that if
diff --git a/gdk4/src/subclass/content_provider.rs b/gdk4/src/subclass/content_provider.rs
index 50c11a0798c9..a9a720632178 100644
--- a/gdk4/src/subclass/content_provider.rs
+++ b/gdk4/src/subclass/content_provider.rs
@@ -9,7 +9,7 @@ use glib::{translate::*, Value};
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Clipboard, ContentFormats, ContentProvider};
 
-pub trait ContentProviderImpl: ContentProviderImplExt + ObjectImpl {
+pub trait ContentProviderImpl: ObjectImpl + ObjectSubclass<Type: IsA<ContentProvider>> {
     fn content_changed(&self) {
         self.parent_content_changed()
     }
@@ -44,12 +44,7 @@ pub trait ContentProviderImpl: ContentProviderImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ContentProviderImplExt> Sealed for T {}
-}
-
-pub trait ContentProviderImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ContentProviderImplExt: ContentProviderImpl {
     fn parent_content_changed(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gdk4/src/subclass/paintable.rs b/gdk4/src/subclass/paintable.rs
index c0bb7451a9b9..33735986bfdc 100644
--- a/gdk4/src/subclass/paintable.rs
+++ b/gdk4/src/subclass/paintable.rs
@@ -8,7 +8,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Paintable, PaintableFlags, Snapshot};
 
-pub trait PaintableImpl: PaintableImplExt + ObjectImpl {
+pub trait PaintableImpl: ObjectImpl + ObjectSubclass<Type: IsA<Paintable>> {
     #[doc(alias = "get_current_image")]
     fn current_image(&self) -> Paintable {
         self.parent_current_image()
@@ -37,12 +37,7 @@ pub trait PaintableImpl: PaintableImplExt + ObjectImpl {
     fn snapshot(&self, snapshot: &Snapshot, width: f64, height: f64);
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::PaintableImplExt> Sealed for T {}
-}
-
-pub trait PaintableImplExt: sealed::Sealed + ObjectSubclass {
+pub trait PaintableImplExt: PaintableImpl {
     fn parent_current_image(&self) -> Paintable {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/accessible.rs b/gtk4/src/subclass/accessible.rs
index 48ef5175f3de..55053c2f544f 100644
--- a/gtk4/src/subclass/accessible.rs
+++ b/gtk4/src/subclass/accessible.rs
@@ -12,7 +12,7 @@ use crate::{
     ffi, prelude::*, subclass::prelude::*, ATContext, Accessible, AccessiblePlatformState,
 };
 
-pub trait AccessibleImpl: ObjectImpl {
+pub trait AccessibleImpl: ObjectImpl + ObjectSubclass<Type: IsA<Accessible>> {
     #[doc(alias = "get_platform_state")]
     fn platform_state(&self, state: AccessiblePlatformState) -> bool {
         self.parent_platform_state(state)
@@ -44,12 +44,7 @@ pub trait AccessibleImpl: ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::AccessibleImplExt> Sealed for T {}
-}
-
-pub trait AccessibleImplExt: sealed::Sealed + ObjectSubclass {
+pub trait AccessibleImplExt: AccessibleImpl {
     fn parent_platform_state(&self, state: AccessiblePlatformState) -> bool {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/accessible_range.rs b/gtk4/src/subclass/accessible_range.rs
index c3cf121c7bc9..0fd8106faad6 100644
--- a/gtk4/src/subclass/accessible_range.rs
+++ b/gtk4/src/subclass/accessible_range.rs
@@ -8,18 +8,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, AccessibleRange};
 
-pub trait AccessibleRangeImpl: WidgetImpl {
+pub trait AccessibleRangeImpl: AccessibleImpl + ObjectSubclass<Type: IsA<AccessibleRange>> {
     fn set_current_value(&self, value: f64) -> bool {
         self.parent_set_current_value(value)
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::AccessibleRangeImplExt> Sealed for T {}
-}
-
-pub trait AccessibleRangeImplExt: sealed::Sealed + ObjectSubclass {
+pub trait AccessibleRangeImplExt: AccessibleRangeImpl {
     // Returns true if the operation was performed, false otherwise
     fn parent_set_current_value(&self, value: f64) -> bool {
         unsafe {
diff --git a/gtk4/src/subclass/actionable.rs b/gtk4/src/subclass/actionable.rs
index bb0980c99547..cfcfb65cadef 100644
--- a/gtk4/src/subclass/actionable.rs
+++ b/gtk4/src/subclass/actionable.rs
@@ -8,7 +8,7 @@ use glib::{translate::*, GString, Variant};
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Actionable};
 
-pub trait ActionableImpl: WidgetImpl {
+pub trait ActionableImpl: WidgetImpl + ObjectSubclass<Type: IsA<Actionable>> {
     #[doc(alias = "get_action_name")]
     fn action_name(&self) -> Option<GString>;
     #[doc(alias = "get_action_target_value")]
@@ -17,12 +17,7 @@ pub trait ActionableImpl: WidgetImpl {
     fn set_action_target_value(&self, value: Option<&Variant>);
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ActionableImplExt> Sealed for T {}
-}
-
-pub trait ActionableImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ActionableImplExt: ActionableImpl {
     fn parent_action_name(&self) -> Option<GString> {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/adjustment.rs b/gtk4/src/subclass/adjustment.rs
index a2cc814f12e6..c50da39e712c 100644
--- a/gtk4/src/subclass/adjustment.rs
+++ b/gtk4/src/subclass/adjustment.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Adjustment};
 
-pub trait AdjustmentImpl: AdjustmentImplExt + ObjectImpl {
+pub trait AdjustmentImpl: ObjectImpl + ObjectSubclass<Type: IsA<Adjustment>> {
     fn changed(&self) {
         self.parent_changed()
     }
@@ -17,12 +17,7 @@ pub trait AdjustmentImpl: AdjustmentImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::AdjustmentImplExt> Sealed for T {}
-}
-
-pub trait AdjustmentImplExt: sealed::Sealed + ObjectSubclass {
+pub trait AdjustmentImplExt: AdjustmentImpl {
     fn parent_changed(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/application.rs b/gtk4/src/subclass/application.rs
index 9a9fa76997fd..1e9e726ef168 100644
--- a/gtk4/src/subclass/application.rs
+++ b/gtk4/src/subclass/application.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Application, Window};
 
-pub trait GtkApplicationImpl: GtkApplicationImplExt + ApplicationImpl {
+pub trait GtkApplicationImpl: ApplicationImpl + ObjectSubclass<Type: IsA<Application>> {
     fn window_added(&self, window: &Window) {
         self.parent_window_added(window)
     }
@@ -17,12 +17,7 @@ pub trait GtkApplicationImpl: GtkApplicationImplExt + ApplicationImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::GtkApplicationImplExt> Sealed for T {}
-}
-
-pub trait GtkApplicationImplExt: sealed::Sealed + ObjectSubclass {
+pub trait GtkApplicationImplExt: GtkApplicationImpl {
     fn parent_window_added(&self, window: &Window) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/application_window.rs b/gtk4/src/subclass/application_window.rs
index 525adf29b059..68460db56e40 100644
--- a/gtk4/src/subclass/application_window.rs
+++ b/gtk4/src/subclass/application_window.rs
@@ -4,8 +4,11 @@
 //! Traits intended for subclassing
 //! [`ApplicationWindow`](crate::ApplicationWindow).
 
-use crate::{subclass::prelude::*, ApplicationWindow};
+use crate::{prelude::*, subclass::prelude::*, ApplicationWindow};
 
-pub trait ApplicationWindowImpl: WindowImpl + 'static {}
+pub trait ApplicationWindowImpl:
+    WindowImpl + ObjectSubclass<Type: IsA<ApplicationWindow>> + 'static
+{
+}
 
 unsafe impl<T: ApplicationWindowImpl> IsSubclassable<T> for ApplicationWindow {}
diff --git a/gtk4/src/subclass/box_.rs b/gtk4/src/subclass/box_.rs
index 4d540bec45d3..ed65edc1a3e2 100644
--- a/gtk4/src/subclass/box_.rs
+++ b/gtk4/src/subclass/box_.rs
@@ -3,8 +3,8 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`Box`](crate::Box).
 
-use crate::{subclass::prelude::*, Box};
+use crate::{prelude::*, subclass::prelude::*, Box};
 
-pub trait BoxImpl: WidgetImpl {}
+pub trait BoxImpl: WidgetImpl + ObjectSubclass<Type: IsA<Box>> {}
 
 unsafe impl<T: BoxImpl> IsSubclassable<T> for Box {}
diff --git a/gtk4/src/subclass/buildable.rs b/gtk4/src/subclass/buildable.rs
index 5e10e5142f7d..8bf24aea97fe 100644
--- a/gtk4/src/subclass/buildable.rs
+++ b/gtk4/src/subclass/buildable.rs
@@ -10,7 +10,7 @@ use glib::{translate::*, GString, Object, Quark, Value};
 use super::PtrHolder;
 use crate::{ffi, prelude::*, subclass::prelude::*, Buildable, Builder};
 
-pub trait BuildableImpl: ObjectImpl {
+pub trait BuildableImpl: ObjectImpl + ObjectSubclass<Type: IsA<Buildable>> {
     fn set_id(&self, id: &str) {
         self.parent_set_id(id)
     }
@@ -59,12 +59,7 @@ pub trait BuildableImpl: ObjectImpl {
     // );
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::BuildableImplExt> Sealed for T {}
-}
-
-pub trait BuildableImplExt: sealed::Sealed + ObjectSubclass {
+pub trait BuildableImplExt: BuildableImpl {
     fn parent_set_id(&self, id: &str) {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/builder_scope.rs b/gtk4/src/subclass/builder_scope.rs
index 6d49b3a7f373..db04f451c41a 100644
--- a/gtk4/src/subclass/builder_scope.rs
+++ b/gtk4/src/subclass/builder_scope.rs
@@ -11,11 +11,11 @@ use crate::{
     BuilderScope,
 };
 
-pub trait BuilderCScopeImpl: BuilderScopeImpl {}
+pub trait BuilderCScopeImpl: BuilderScopeImpl + ObjectSubclass<Type: IsA<BuilderCScope>> {}
 
 unsafe impl<T: BuilderCScopeImpl> IsSubclassable<T> for BuilderCScope {}
 
-pub trait BuilderScopeImpl: ObjectImpl {
+pub trait BuilderScopeImpl: ObjectImpl + ObjectSubclass<Type: IsA<BuilderScope>> {
     #[doc(alias = "get_type_from_name")]
     fn type_from_name(&self, builder: &Builder, type_name: &str) -> glib::Type {
         self.parent_type_from_name(builder, type_name)
@@ -35,12 +35,7 @@ pub trait BuilderScopeImpl: ObjectImpl {
     ) -> Result<glib::Closure, glib::Error>;
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::BuilderScopeImplExt> Sealed for T {}
-}
-
-pub trait BuilderScopeImplExt: sealed::Sealed + ObjectSubclass {
+pub trait BuilderScopeImplExt: BuilderScopeImpl {
     fn parent_type_from_name(&self, builder: &Builder, type_name: &str) -> glib::Type {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/button.rs b/gtk4/src/subclass/button.rs
index 68750d3da9c9..f62817264d97 100644
--- a/gtk4/src/subclass/button.rs
+++ b/gtk4/src/subclass/button.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Button};
 
-pub trait ButtonImpl: ButtonImplExt + WidgetImpl {
+pub trait ButtonImpl: WidgetImpl + ObjectSubclass<Type: IsA<Button>> {
     fn activate(&self) {
         self.parent_activate()
     }
@@ -17,12 +17,7 @@ pub trait ButtonImpl: ButtonImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ButtonImplExt> Sealed for T {}
-}
-
-pub trait ButtonImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ButtonImplExt: ButtonImpl {
     fn parent_activate(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/cell_area.rs b/gtk4/src/subclass/cell_area.rs
index 8e50c3423a1f..a3e5e3f910e8 100644
--- a/gtk4/src/subclass/cell_area.rs
+++ b/gtk4/src/subclass/cell_area.rs
@@ -63,7 +63,7 @@ impl CellCallbackAllocate {
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellAreaImpl: CellAreaImplExt + ObjectImpl {
+pub trait CellAreaImpl: ObjectImpl + ObjectSubclass<Type: IsA<CellArea>> {
     fn cell_properties() -> &'static [ParamSpec] {
         &[]
     }
@@ -219,14 +219,9 @@ pub trait CellAreaImpl: CellAreaImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::CellAreaImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellAreaImplExt: sealed::Sealed + ObjectSubclass {
+pub trait CellAreaImplExt: CellAreaImpl {
     // Returns true if the area was successfully activated
     fn parent_activate<P: IsA<CellAreaContext>, W: IsA<Widget>>(
         &self,
@@ -956,4 +951,4 @@ pub unsafe trait CellAreaClassExt: ClassStruct {
     }
 }
 
-unsafe impl<T: ClassStruct> CellAreaClassExt for T where T::Type: CellAreaImpl {}
+unsafe impl<T: ClassStruct> CellAreaClassExt for T {}
diff --git a/gtk4/src/subclass/cell_area_context.rs b/gtk4/src/subclass/cell_area_context.rs
index a2b8c7bc3529..1f5b60efa109 100644
--- a/gtk4/src/subclass/cell_area_context.rs
+++ b/gtk4/src/subclass/cell_area_context.rs
@@ -11,7 +11,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, CellAreaContext};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellAreaContextImpl: CellAreaContextImplExt + ObjectImpl {
+pub trait CellAreaContextImpl: ObjectImpl + ObjectSubclass<Type: IsA<CellAreaContext>> {
     fn reset(&self) {
         self.parent_reset()
     }
@@ -29,14 +29,9 @@ pub trait CellAreaContextImpl: CellAreaContextImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::CellAreaContextImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellAreaContextImplExt: sealed::Sealed + ObjectSubclass {
+pub trait CellAreaContextImplExt: CellAreaContextImpl {
     fn parent_reset(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/cell_editable.rs b/gtk4/src/subclass/cell_editable.rs
index 7ec83693d62c..937b4ce66dc7 100644
--- a/gtk4/src/subclass/cell_editable.rs
+++ b/gtk4/src/subclass/cell_editable.rs
@@ -10,7 +10,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, CellEditable};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellEditableImpl: ObjectImpl {
+pub trait CellEditableImpl: ObjectImpl + ObjectSubclass<Type: IsA<CellEditable>> {
     fn editing_done(&self) {
         self.parent_editing_done()
     }
@@ -24,14 +24,9 @@ pub trait CellEditableImpl: ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::CellEditableImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellEditableImplExt: sealed::Sealed + ObjectSubclass {
+pub trait CellEditableImplExt: CellEditableImpl {
     fn parent_editing_done(&self) {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/cell_layout.rs b/gtk4/src/subclass/cell_layout.rs
index 427d48b3d039..1fd4896f81b4 100644
--- a/gtk4/src/subclass/cell_layout.rs
+++ b/gtk4/src/subclass/cell_layout.rs
@@ -53,7 +53,7 @@ impl Drop for CellLayoutDataCallback {
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellLayoutImpl: ObjectImpl {
+pub trait CellLayoutImpl: ObjectImpl + ObjectSubclass<Type: IsA<CellLayout>> {
     fn add_attribute<R: IsA<CellRenderer>>(&self, cell: &R, attribute: &str, column: i32) {
         self.parent_add_attribute(cell, attribute, column)
     }
@@ -96,14 +96,9 @@ pub trait CellLayoutImpl: ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::CellLayoutImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellLayoutImplExt: sealed::Sealed + ObjectSubclass {
+pub trait CellLayoutImplExt: CellLayoutImpl {
     fn parent_add_attribute<R: IsA<CellRenderer>>(&self, cell: &R, attribute: &str, column: i32) {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/cell_renderer.rs b/gtk4/src/subclass/cell_renderer.rs
index 9a8856b78647..7f88c27906c8 100644
--- a/gtk4/src/subclass/cell_renderer.rs
+++ b/gtk4/src/subclass/cell_renderer.rs
@@ -15,7 +15,7 @@ use crate::{
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellRendererImpl: CellRendererImplExt + ObjectImpl {
+pub trait CellRendererImpl: ObjectImpl + ObjectSubclass<Type: IsA<CellRenderer>> {
     fn activate<P: IsA<Widget>>(
         &self,
         event: Option<&gdk::Event>,
@@ -95,14 +95,9 @@ pub trait CellRendererImpl: CellRendererImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::CellRendererImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellRendererImplExt: sealed::Sealed + ObjectSubclass {
+pub trait CellRendererImplExt: CellRendererImpl {
     fn parent_request_mode(&self) -> SizeRequestMode {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/cell_renderer_text.rs b/gtk4/src/subclass/cell_renderer_text.rs
index d85e8fa03305..fdfb0d91865b 100644
--- a/gtk4/src/subclass/cell_renderer_text.rs
+++ b/gtk4/src/subclass/cell_renderer_text.rs
@@ -10,20 +10,17 @@ use crate::{ffi, prelude::*, subclass::prelude::*, CellRendererText};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellRendererTextImpl: CellRendererTextImplExt + CellRendererImpl {
+pub trait CellRendererTextImpl:
+    CellRendererImpl + ObjectSubclass<Type: IsA<CellRendererText>>
+{
     fn edited(&self, path: &str, new_text: &str) {
         self.parent_edited(path, new_text);
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::CellRendererTextImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait CellRendererTextImplExt: sealed::Sealed + ObjectSubclass {
+pub trait CellRendererTextImplExt: CellRendererTextImpl {
     fn parent_edited(&self, path: &str, new_text: &str) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/check_button.rs b/gtk4/src/subclass/check_button.rs
index 5b9e4d508e7d..c7ac02eaeef4 100644
--- a/gtk4/src/subclass/check_button.rs
+++ b/gtk4/src/subclass/check_button.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, CheckButton};
 
-pub trait CheckButtonImpl: CheckButtonImplExt + WidgetImpl {
+pub trait CheckButtonImpl: WidgetImpl + ObjectSubclass<Type: IsA<CheckButton>> {
     fn toggled(&self) {
         self.parent_toggled()
     }
@@ -19,12 +19,7 @@ pub trait CheckButtonImpl: CheckButtonImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::CheckButtonImplExt> Sealed for T {}
-}
-
-pub trait CheckButtonImplExt: sealed::Sealed + ObjectSubclass {
+pub trait CheckButtonImplExt: CheckButtonImpl {
     fn parent_toggled(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/color_chooser.rs b/gtk4/src/subclass/color_chooser.rs
index 00c836dbc114..0cd35eecfeee 100644
--- a/gtk4/src/subclass/color_chooser.rs
+++ b/gtk4/src/subclass/color_chooser.rs
@@ -11,7 +11,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, ColorChooser, Orientation};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait ColorChooserImpl: ObjectImpl {
+pub trait ColorChooserImpl: ObjectImpl + ObjectSubclass<Type: IsA<ColorChooser>> {
     fn add_palette(&self, orientation: Orientation, colors_per_line: i32, colors: &[RGBA]) {
         self.parent_add_palette(orientation, colors_per_line, colors);
     }
@@ -25,14 +25,9 @@ pub trait ColorChooserImpl: ObjectImpl {
     fn set_rgba(&self, rgba: RGBA);
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ColorChooserImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait ColorChooserImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ColorChooserImplExt: ColorChooserImpl {
     fn parent_add_palette(&self, orientation: Orientation, colors_per_line: i32, colors: &[RGBA]) {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/combo_box.rs b/gtk4/src/subclass/combo_box.rs
index a88d7399e776..e67a7150a4c5 100644
--- a/gtk4/src/subclass/combo_box.rs
+++ b/gtk4/src/subclass/combo_box.rs
@@ -9,7 +9,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, ComboBox};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait ComboBoxImpl: ComboBoxImplExt + WidgetImpl {
+pub trait ComboBoxImpl: WidgetImpl + ObjectSubclass<Type: IsA<ComboBox>> {
     #[cfg(feature = "v4_6")]
     #[cfg_attr(docsrs, doc(cfg(feature = "v4_6")))]
     fn activate(&self) {
@@ -23,14 +23,9 @@ pub trait ComboBoxImpl: ComboBoxImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ComboBoxImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait ComboBoxImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ComboBoxImplExt: ComboBoxImpl {
     #[cfg(feature = "v4_6")]
     #[cfg_attr(docsrs, doc(cfg(feature = "v4_6")))]
     fn parent_activate(&self) {
diff --git a/gtk4/src/subclass/dialog.rs b/gtk4/src/subclass/dialog.rs
index 2fb77162f9cd..3020c30e61f9 100644
--- a/gtk4/src/subclass/dialog.rs
+++ b/gtk4/src/subclass/dialog.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Dialog, ResponseType};
 
-pub trait DialogImpl: DialogImplExt + WindowImpl {
+pub trait DialogImpl: WindowImpl + ObjectSubclass<Type: IsA<Dialog>> {
     fn response(&self, response: ResponseType) {
         self.parent_response(response)
     }
@@ -17,12 +17,7 @@ pub trait DialogImpl: DialogImplExt + WindowImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::DialogImplExt> Sealed for T {}
-}
-
-pub trait DialogImplExt: sealed::Sealed + ObjectSubclass {
+pub trait DialogImplExt: DialogImpl {
     fn parent_response(&self, response: ResponseType) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/drawing_area.rs b/gtk4/src/subclass/drawing_area.rs
index 3d4ef8b293d5..b941aef4db34 100644
--- a/gtk4/src/subclass/drawing_area.rs
+++ b/gtk4/src/subclass/drawing_area.rs
@@ -7,17 +7,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, DrawingArea};
 
-pub trait DrawingAreaImpl: DrawingAreaImplExt + WidgetImpl {
+pub trait DrawingAreaImpl: WidgetImpl + ObjectSubclass<Type: IsA<DrawingArea>> {
     fn resize(&self, width: i32, height: i32) {
         self.parent_resize(width, height)
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::DrawingAreaImplExt> Sealed for T {}
-}
-pub trait DrawingAreaImplExt: sealed::Sealed + ObjectSubclass {
+pub trait DrawingAreaImplExt: DrawingAreaImpl {
     fn parent_resize(&self, width: i32, height: i32) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/editable.rs b/gtk4/src/subclass/editable.rs
index 6a418ab9291e..1e6e6675e7c0 100644
--- a/gtk4/src/subclass/editable.rs
+++ b/gtk4/src/subclass/editable.rs
@@ -10,7 +10,7 @@ use libc::{c_char, c_int};
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Editable};
 
-pub trait EditableImpl: WidgetImpl {
+pub trait EditableImpl: WidgetImpl + ObjectSubclass<Type: IsA<Editable>> {
     fn insert_text(&self, text: &str, length: i32, position: &mut i32) {
         self.parent_insert_text(text, length, position);
     }
@@ -51,12 +51,7 @@ pub trait EditableImpl: WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::EditableImplExt> Sealed for T {}
-}
-
-pub trait EditableImplExt: sealed::Sealed + ObjectSubclass {
+pub trait EditableImplExt: EditableImpl {
     #[doc(alias = "gtk_editable_delegate_get_property")]
     fn delegate_get_property(
         &self,
diff --git a/gtk4/src/subclass/entry.rs b/gtk4/src/subclass/entry.rs
index 321a087022f5..a507df9b89a9 100644
--- a/gtk4/src/subclass/entry.rs
+++ b/gtk4/src/subclass/entry.rs
@@ -7,18 +7,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Entry};
 
-pub trait EntryImpl: EntryImplExt + WidgetImpl {
+pub trait EntryImpl: WidgetImpl + ObjectSubclass<Type: IsA<Entry>> {
     fn activate(&self) {
         self.parent_activate()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::EntryImplExt> Sealed for T {}
-}
-
-pub trait EntryImplExt: sealed::Sealed + ObjectSubclass {
+pub trait EntryImplExt: EntryImpl {
     fn parent_activate(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/entry_buffer.rs b/gtk4/src/subclass/entry_buffer.rs
index b252566f5366..b0d38a47a95a 100644
--- a/gtk4/src/subclass/entry_buffer.rs
+++ b/gtk4/src/subclass/entry_buffer.rs
@@ -9,7 +9,7 @@ use glib::{translate::*, GString};
 use super::PtrHolder;
 use crate::{ffi, prelude::*, subclass::prelude::*, EntryBuffer};
 
-pub trait EntryBufferImpl: EntryBufferImplExt + ObjectImpl {
+pub trait EntryBufferImpl: ObjectImpl + ObjectSubclass<Type: IsA<EntryBuffer>> {
     fn delete_text(&self, position: u32, n_chars: Option<u32>) -> u32 {
         self.parent_delete_text(position, n_chars)
     }
@@ -36,12 +36,7 @@ pub trait EntryBufferImpl: EntryBufferImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::EntryBufferImplExt> Sealed for T {}
-}
-
-pub trait EntryBufferImplExt: sealed::Sealed + ObjectSubclass {
+pub trait EntryBufferImplExt: EntryBufferImpl {
     fn parent_delete_text(&self, position: u32, n_chars: Option<u32>) -> u32 {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/filter.rs b/gtk4/src/subclass/filter.rs
index fac41809e392..3b357c0960dc 100644
--- a/gtk4/src/subclass/filter.rs
+++ b/gtk4/src/subclass/filter.rs
@@ -7,7 +7,7 @@ use glib::{translate::*, Object};
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Filter, FilterMatch};
 
-pub trait FilterImpl: FilterImplExt + ObjectImpl {
+pub trait FilterImpl: ObjectImpl + ObjectSubclass<Type: IsA<Filter>> {
     #[doc(alias = "get_strictness")]
     fn strictness(&self) -> FilterMatch {
         self.parent_strictness()
@@ -17,12 +17,7 @@ pub trait FilterImpl: FilterImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::FilterImplExt> Sealed for T {}
-}
-
-pub trait FilterImplExt: sealed::Sealed + ObjectSubclass {
+pub trait FilterImplExt: FilterImpl {
     fn parent_strictness(&self) -> FilterMatch {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/fixed.rs b/gtk4/src/subclass/fixed.rs
index 2d14ccb310e3..3fbf6dace02c 100644
--- a/gtk4/src/subclass/fixed.rs
+++ b/gtk4/src/subclass/fixed.rs
@@ -3,8 +3,8 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`Fixed`](crate::Fixed).
 
-use crate::{subclass::prelude::*, Fixed};
+use crate::{prelude::*, subclass::prelude::*, Fixed};
 
-pub trait FixedImpl: WidgetImpl {}
+pub trait FixedImpl: WidgetImpl + ObjectSubclass<Type: IsA<Fixed>> {}
 
 unsafe impl<T: FixedImpl> IsSubclassable<T> for Fixed {}
diff --git a/gtk4/src/subclass/flow_box_child.rs b/gtk4/src/subclass/flow_box_child.rs
index dde047d4acaa..77866b1f4f2a 100644
--- a/gtk4/src/subclass/flow_box_child.rs
+++ b/gtk4/src/subclass/flow_box_child.rs
@@ -7,18 +7,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, FlowBoxChild};
 
-pub trait FlowBoxChildImpl: FlowBoxChildImplExt + WidgetImpl {
+pub trait FlowBoxChildImpl: WidgetImpl + ObjectSubclass<Type: IsA<FlowBoxChild>> {
     fn activate(&self) {
         self.parent_activate()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::FlowBoxChildImplExt> Sealed for T {}
-}
-
-pub trait FlowBoxChildImplExt: sealed::Sealed + ObjectSubclass {
+pub trait FlowBoxChildImplExt: FlowBoxChildImpl {
     fn parent_activate(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/font_chooser.rs b/gtk4/src/subclass/font_chooser.rs
index c232860f5110..a4723211a94a 100644
--- a/gtk4/src/subclass/font_chooser.rs
+++ b/gtk4/src/subclass/font_chooser.rs
@@ -49,7 +49,7 @@ impl Drop for FilterCallback {
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait FontChooserImpl: ObjectImpl {
+pub trait FontChooserImpl: ObjectImpl + ObjectSubclass<Type: IsA<FontChooser>> {
     fn font_family(&self) -> Option<FontFamily> {
         self.parent_font_family()
     }
@@ -79,14 +79,9 @@ pub trait FontChooserImpl: ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::FontChooserImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait FontChooserImplExt: sealed::Sealed + ObjectSubclass {
+pub trait FontChooserImplExt: FontChooserImpl {
     fn parent_font_family(&self) -> Option<FontFamily> {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/frame.rs b/gtk4/src/subclass/frame.rs
index 0eed42525de5..d5c8e5352a23 100644
--- a/gtk4/src/subclass/frame.rs
+++ b/gtk4/src/subclass/frame.rs
@@ -9,7 +9,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, Allocation, Frame};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait FrameImpl: FrameImplExt + WidgetImpl {
+pub trait FrameImpl: WidgetImpl + ObjectSubclass<Type: IsA<Frame>> {
     fn compute_child_allocation(&self) -> Allocation {
         self.parent_compute_child_allocation()
     }
@@ -17,7 +17,7 @@ pub trait FrameImpl: FrameImplExt + WidgetImpl {
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait FrameImplExt: ObjectSubclass {
+pub trait FrameImplExt: FrameImpl {
     fn parent_compute_child_allocation(&self) -> Allocation {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/gl_area.rs b/gtk4/src/subclass/gl_area.rs
index 9c7e779285fd..dd1dcd8e1b69 100644
--- a/gtk4/src/subclass/gl_area.rs
+++ b/gtk4/src/subclass/gl_area.rs
@@ -9,7 +9,7 @@ use glib::translate::*;
 use crate::{ffi, prelude::*, subclass::prelude::*, GLArea};
 
 #[allow(clippy::upper_case_acronyms)]
-pub trait GLAreaImpl: GLAreaImplExt + WidgetImpl {
+pub trait GLAreaImpl: WidgetImpl + ObjectSubclass<Type: IsA<GLArea>> {
     fn create_context(&self) -> Option<GLContext> {
         self.parent_create_context()
     }
@@ -23,13 +23,8 @@ pub trait GLAreaImpl: GLAreaImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::GLAreaImplExt> Sealed for T {}
-}
-
 #[allow(clippy::upper_case_acronyms)]
-pub trait GLAreaImplExt: sealed::Sealed + ObjectSubclass {
+pub trait GLAreaImplExt: GLAreaImpl {
     fn parent_create_context(&self) -> Option<GLContext> {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/grid.rs b/gtk4/src/subclass/grid.rs
index 56c5c5dc4ea6..883582274804 100644
--- a/gtk4/src/subclass/grid.rs
+++ b/gtk4/src/subclass/grid.rs
@@ -3,8 +3,8 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`Grid`](crate::Grid).
 
-use crate::{subclass::prelude::*, Grid};
+use crate::{prelude::*, subclass::prelude::*, Grid};
 
-pub trait GridImpl: WidgetImpl {}
+pub trait GridImpl: WidgetImpl + ObjectSubclass<Type: IsA<Grid>> {}
 
 unsafe impl<T: GridImpl> IsSubclassable<T> for Grid {}
diff --git a/gtk4/src/subclass/im_context.rs b/gtk4/src/subclass/im_context.rs
index 979619aa850d..fea3861d7d35 100644
--- a/gtk4/src/subclass/im_context.rs
+++ b/gtk4/src/subclass/im_context.rs
@@ -9,7 +9,7 @@ use pango::AttrList;
 use crate::{ffi, prelude::*, subclass::prelude::*, IMContext, Widget};
 
 #[allow(clippy::upper_case_acronyms)]
-pub trait IMContextImpl: IMContextImplExt + ObjectImpl {
+pub trait IMContextImpl: ObjectImpl + ObjectSubclass<Type: IsA<IMContext>> {
     fn commit(&self, string: &str) {
         self.parent_commit(string)
     }
@@ -74,13 +74,8 @@ pub trait IMContextImpl: IMContextImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::IMContextImplExt> Sealed for T {}
-}
-
 #[allow(clippy::upper_case_acronyms)]
-pub trait IMContextImplExt: sealed::Sealed + ObjectSubclass {
+pub trait IMContextImplExt: IMContextImpl {
     fn parent_commit(&self, string: &str) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/layout_child.rs b/gtk4/src/subclass/layout_child.rs
index 3aed155484e9..f105a656ac3d 100644
--- a/gtk4/src/subclass/layout_child.rs
+++ b/gtk4/src/subclass/layout_child.rs
@@ -3,9 +3,9 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`LayoutChild`](crate::LayoutChild).
 
-use crate::{subclass::prelude::*, LayoutChild};
+use crate::{prelude::*, subclass::prelude::*, LayoutChild};
 
-pub trait LayoutChildImpl: ObjectImpl {}
+pub trait LayoutChildImpl: ObjectImpl + ObjectSubclass<Type: IsA<LayoutChild>> {}
 
 unsafe impl<T: LayoutChildImpl> IsSubclassable<T> for LayoutChild {
     fn class_init(class: &mut glib::Class<Self>) {
diff --git a/gtk4/src/subclass/layout_manager.rs b/gtk4/src/subclass/layout_manager.rs
index 5d3e97b0658b..a953bfd77c5d 100644
--- a/gtk4/src/subclass/layout_manager.rs
+++ b/gtk4/src/subclass/layout_manager.rs
@@ -11,7 +11,7 @@ use crate::{
     SizeRequestMode, Widget,
 };
 
-pub trait LayoutManagerImpl: LayoutManagerImplExt + ObjectImpl {
+pub trait LayoutManagerImpl: ObjectImpl + ObjectSubclass<Type: IsA<LayoutManager>> {
     fn allocate(&self, widget: &Widget, width: i32, height: i32, baseline: i32) {
         self.parent_allocate(widget, width, height, baseline)
     }
@@ -48,12 +48,7 @@ pub trait LayoutManagerImpl: LayoutManagerImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::LayoutManagerImplExt> Sealed for T {}
-}
-
-pub trait LayoutManagerImplExt: sealed::Sealed + ObjectSubclass {
+pub trait LayoutManagerImplExt: LayoutManagerImpl {
     fn parent_allocate(&self, widget: &Widget, width: i32, height: i32, baseline: i32) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/list_box_row.rs b/gtk4/src/subclass/list_box_row.rs
index 241975274b94..a07ec9cfd441 100644
--- a/gtk4/src/subclass/list_box_row.rs
+++ b/gtk4/src/subclass/list_box_row.rs
@@ -7,18 +7,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, ListBoxRow};
 
-pub trait ListBoxRowImpl: ListBoxRowImplExt + WidgetImpl {
+pub trait ListBoxRowImpl: WidgetImpl + ObjectSubclass<Type: IsA<ListBoxRow>> {
     fn activate(&self) {
         self.parent_activate()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ListBoxRowImplExt> Sealed for T {}
-}
-
-pub trait ListBoxRowImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ListBoxRowImplExt: ListBoxRowImpl {
     fn parent_activate(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/media_file.rs b/gtk4/src/subclass/media_file.rs
index c97c2335af35..b96d4dc05b57 100644
--- a/gtk4/src/subclass/media_file.rs
+++ b/gtk4/src/subclass/media_file.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, MediaFile};
 
-pub trait MediaFileImpl: MediaFileImplExt + MediaStreamImpl {
+pub trait MediaFileImpl: MediaStreamImpl + ObjectSubclass<Type: IsA<MediaFile>> {
     fn close(&self) {
         self.parent_close()
     }
@@ -16,12 +16,7 @@ pub trait MediaFileImpl: MediaFileImplExt + MediaStreamImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::MediaFileImplExt> Sealed for T {}
-}
-
-pub trait MediaFileImplExt: sealed::Sealed + ObjectSubclass {
+pub trait MediaFileImplExt: MediaFileImpl {
     fn parent_close(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/media_stream.rs b/gtk4/src/subclass/media_stream.rs
index d0786b0c6da8..9dccee4e5b93 100644
--- a/gtk4/src/subclass/media_stream.rs
+++ b/gtk4/src/subclass/media_stream.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, MediaStream};
 
-pub trait MediaStreamImpl: MediaStreamImplExt + ObjectImpl {
+pub trait MediaStreamImpl: ObjectImpl + ObjectSubclass<Type: IsA<MediaStream>> {
     fn pause(&self) {
         self.parent_pause()
     }
@@ -33,12 +33,7 @@ pub trait MediaStreamImpl: MediaStreamImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::MediaStreamImplExt> Sealed for T {}
-}
-
-pub trait MediaStreamImplExt: sealed::Sealed + ObjectSubclass {
+pub trait MediaStreamImplExt: MediaStreamImpl {
     fn parent_pause(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/native_dialog.rs b/gtk4/src/subclass/native_dialog.rs
index 5cda1e37efca..0281ee2e84f1 100644
--- a/gtk4/src/subclass/native_dialog.rs
+++ b/gtk4/src/subclass/native_dialog.rs
@@ -9,7 +9,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, NativeDialog, ResponseType};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait NativeDialogImpl: NativeDialogImplExt + ObjectImpl {
+pub trait NativeDialogImpl: ObjectImpl + ObjectSubclass<Type: IsA<NativeDialog>> {
     fn response(&self, response: ResponseType) {
         self.parent_response(response)
     }
@@ -23,14 +23,9 @@ pub trait NativeDialogImpl: NativeDialogImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::NativeDialogImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait NativeDialogImplExt: sealed::Sealed + ObjectSubclass {
+pub trait NativeDialogImplExt: NativeDialogImpl {
     fn parent_response(&self, response: ResponseType) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/orientable.rs b/gtk4/src/subclass/orientable.rs
index 8cc34827af37..362ecbc5e28a 100644
--- a/gtk4/src/subclass/orientable.rs
+++ b/gtk4/src/subclass/orientable.rs
@@ -4,8 +4,8 @@
 //! Traits intended for implementing the [`Orientable`](crate::Orientable)
 //! interface.
 
-use crate::{subclass::prelude::*, Orientable};
+use crate::{prelude::*, subclass::prelude::*, Orientable};
 
-pub trait OrientableImpl: WidgetImpl {}
+pub trait OrientableImpl: ObjectImpl + ObjectSubclass<Type: IsA<Orientable>> {}
 
 unsafe impl<T: OrientableImpl> IsImplementable<T> for Orientable {}
diff --git a/gtk4/src/subclass/popover.rs b/gtk4/src/subclass/popover.rs
index 48d82a9a91b2..28ea7ce745ad 100644
--- a/gtk4/src/subclass/popover.rs
+++ b/gtk4/src/subclass/popover.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Popover};
 
-pub trait PopoverImpl: PopoverImplExt + WidgetImpl {
+pub trait PopoverImpl: WidgetImpl + ObjectSubclass<Type: IsA<Popover>> {
     fn activate_default(&self) {
         self.parent_activate_default()
     }
@@ -17,12 +17,7 @@ pub trait PopoverImpl: PopoverImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::PopoverImplExt> Sealed for T {}
-}
-
-pub trait PopoverImplExt: sealed::Sealed + ObjectSubclass {
+pub trait PopoverImplExt: PopoverImpl {
     fn parent_activate_default(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/print_operation.rs b/gtk4/src/subclass/print_operation.rs
index 45412fcde930..3b33e30e4c3f 100644
--- a/gtk4/src/subclass/print_operation.rs
+++ b/gtk4/src/subclass/print_operation.rs
@@ -10,7 +10,9 @@ use crate::{
     PrintOperationPreview, PrintOperationResult, PrintSettings, Widget, Window,
 };
 
-pub trait PrintOperationImpl: PrintOperationImplExt + PrintOperationPreviewImpl {
+pub trait PrintOperationImpl:
+    PrintOperationPreviewImpl + ObjectSubclass<Type: IsA<PrintOperation>>
+{
     fn begin_print(&self, context: &PrintContext) {
         self.parent_begin_print(context)
     }
@@ -61,12 +63,7 @@ pub trait PrintOperationImpl: PrintOperationImplExt + PrintOperationPreviewImpl
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::PrintOperationImplExt> Sealed for T {}
-}
-
-pub trait PrintOperationImplExt: sealed::Sealed + ObjectSubclass {
+pub trait PrintOperationImplExt: PrintOperationImpl {
     fn parent_begin_print(&self, context: &PrintContext) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/print_operation_preview.rs b/gtk4/src/subclass/print_operation_preview.rs
index 17896262dcfe..f1f161c598c1 100644
--- a/gtk4/src/subclass/print_operation_preview.rs
+++ b/gtk4/src/subclass/print_operation_preview.rs
@@ -10,7 +10,9 @@ use crate::{
     ffi, prelude::*, subclass::prelude::*, PageSetup, PrintContext, PrintOperationPreview,
 };
 
-pub trait PrintOperationPreviewImpl: ObjectImpl {
+pub trait PrintOperationPreviewImpl:
+    ObjectImpl + ObjectSubclass<Type: IsA<PrintOperationPreview>>
+{
     fn ready(&self, context: &PrintContext) {
         self.parent_ready(context)
     }
@@ -24,12 +26,7 @@ pub trait PrintOperationPreviewImpl: ObjectImpl {
     fn end_preview(&self);
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::PrintOperationPreviewImplExt> Sealed for T {}
-}
-
-pub trait PrintOperationPreviewImplExt: sealed::Sealed + ObjectSubclass {
+pub trait PrintOperationPreviewImplExt: PrintOperationPreviewImpl {
     fn parent_ready(&self, context: &PrintContext) {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/range.rs b/gtk4/src/subclass/range.rs
index 1f39c3708d96..e2c3c104f556 100644
--- a/gtk4/src/subclass/range.rs
+++ b/gtk4/src/subclass/range.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Border, Range, ScrollType};
 
-pub trait RangeImpl: RangeImplExt + WidgetImpl {
+pub trait RangeImpl: WidgetImpl + ObjectSubclass<Type: IsA<Range>> {
     fn adjust_bounds(&self, new_value: f64) {
         self.parent_adjust_bounds(new_value)
     }
@@ -30,12 +30,7 @@ pub trait RangeImpl: RangeImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::RangeImplExt> Sealed for T {}
-}
-
-pub trait RangeImplExt: sealed::Sealed + ObjectSubclass {
+pub trait RangeImplExt: RangeImpl {
     fn parent_adjust_bounds(&self, new_value: f64) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/recent_manager.rs b/gtk4/src/subclass/recent_manager.rs
index a4fb70d57970..e699241bccbf 100644
--- a/gtk4/src/subclass/recent_manager.rs
+++ b/gtk4/src/subclass/recent_manager.rs
@@ -7,17 +7,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, RecentManager};
 
-pub trait RecentManagerImpl: RecentManagerImplExt + ObjectImpl {
+pub trait RecentManagerImpl: ObjectImpl + ObjectSubclass<Type: IsA<RecentManager>> {
     fn changed(&self) {
         self.parent_changed()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::RecentManagerImplExt> Sealed for T {}
-}
-pub trait RecentManagerImplExt: sealed::Sealed + ObjectSubclass {
+pub trait RecentManagerImplExt: RecentManagerImpl {
     fn parent_changed(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/scale.rs b/gtk4/src/subclass/scale.rs
index f0df0a6c4306..6c52f6abafdc 100644
--- a/gtk4/src/subclass/scale.rs
+++ b/gtk4/src/subclass/scale.rs
@@ -7,19 +7,14 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Scale};
 
-pub trait ScaleImpl: ScaleImplExt + RangeImpl {
+pub trait ScaleImpl: RangeImpl + ObjectSubclass<Type: IsA<Scale>> {
     #[doc(alias = "get_layout_offsets")]
     fn layout_offsets(&self) -> (i32, i32) {
         self.parent_layout_offsets()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ScaleImplExt> Sealed for T {}
-}
-
-pub trait ScaleImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ScaleImplExt: ScaleImpl {
     fn parent_layout_offsets(&self) -> (i32, i32) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/scale_button.rs b/gtk4/src/subclass/scale_button.rs
index 9add7fbdd674..4606cbd90da5 100644
--- a/gtk4/src/subclass/scale_button.rs
+++ b/gtk4/src/subclass/scale_button.rs
@@ -7,18 +7,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, ScaleButton};
 
-pub trait ScaleButtonImpl: ScaleButtonImplExt + WidgetImpl {
+pub trait ScaleButtonImpl: WidgetImpl + ObjectSubclass<Type: IsA<ScaleButton>> {
     fn value_changed(&self, new_value: f64) {
         self.parent_value_changed(new_value)
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ScaleButtonImplExt> Sealed for T {}
-}
-
-pub trait ScaleButtonImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ScaleButtonImplExt: ScaleButtonImpl {
     fn parent_value_changed(&self, new_value: f64) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/scrollable.rs b/gtk4/src/subclass/scrollable.rs
index 71f26e283c55..c4a88cb06c45 100644
--- a/gtk4/src/subclass/scrollable.rs
+++ b/gtk4/src/subclass/scrollable.rs
@@ -8,19 +8,14 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Border, Scrollable};
 
-pub trait ScrollableImpl: WidgetImpl {
+pub trait ScrollableImpl: WidgetImpl + ObjectSubclass<Type: IsA<Scrollable>> {
     #[doc(alias = "get_border")]
     fn border(&self) -> Option<Border> {
         self.parent_border()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ScrollableImplExt> Sealed for T {}
-}
-
-pub trait ScrollableImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ScrollableImplExt: ScrollableImpl {
     fn parent_border(&self) -> Option<Border> {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/section_model.rs b/gtk4/src/subclass/section_model.rs
index 658554f627f1..5e4a99fc6a8e 100644
--- a/gtk4/src/subclass/section_model.rs
+++ b/gtk4/src/subclass/section_model.rs
@@ -8,19 +8,14 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, SectionModel};
 
-pub trait SectionModelImpl: ListModelImpl {
+pub trait SectionModelImpl: ListModelImpl + ObjectSubclass<Type: IsA<SectionModel>> {
     #[doc(alias = "get_section")]
     fn section(&self, position: u32) -> (u32, u32) {
         self.parent_section(position)
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::SectionModelImplExt> Sealed for T {}
-}
-
-pub trait SectionModelImplExt: sealed::Sealed + ObjectSubclass {
+pub trait SectionModelImplExt: SectionModelImpl {
     fn parent_section(&self, position: u32) -> (u32, u32) {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/selection_model.rs b/gtk4/src/subclass/selection_model.rs
index 1a6b7f8e924e..c858194f90d6 100644
--- a/gtk4/src/subclass/selection_model.rs
+++ b/gtk4/src/subclass/selection_model.rs
@@ -8,7 +8,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Bitset, SelectionModel};
 
-pub trait SelectionModelImpl: ListModelImpl {
+pub trait SelectionModelImpl: ListModelImpl + ObjectSubclass<Type: IsA<SelectionModel>> {
     #[doc(alias = "get_selection_in_range")]
     fn selection_in_range(&self, position: u32, n_items: u32) -> Bitset {
         self.parent_selection_in_range(position, n_items)
@@ -47,12 +47,7 @@ pub trait SelectionModelImpl: ListModelImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::SelectionModelImplExt> Sealed for T {}
-}
-
-pub trait SelectionModelImplExt: sealed::Sealed + ObjectSubclass {
+pub trait SelectionModelImplExt: SelectionModelImpl {
     fn parent_selection_in_range(&self, position: u32, n_items: u32) -> Bitset {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/shortcut_manager.rs b/gtk4/src/subclass/shortcut_manager.rs
index 7e7472df788e..97f0c1f8f0fd 100644
--- a/gtk4/src/subclass/shortcut_manager.rs
+++ b/gtk4/src/subclass/shortcut_manager.rs
@@ -8,7 +8,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, ShortcutController, ShortcutManager};
 
-pub trait ShortcutManagerImpl: ObjectImpl {
+pub trait ShortcutManagerImpl: ObjectImpl + ObjectSubclass<Type: IsA<ShortcutManager>> {
     fn add_controller(&self, controller: &ShortcutController) {
         self.parent_add_controller(controller);
     }
@@ -18,12 +18,7 @@ pub trait ShortcutManagerImpl: ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ShortcutManagerImplExt> Sealed for T {}
-}
-
-pub trait ShortcutManagerImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ShortcutManagerImplExt: ShortcutManagerImpl {
     fn parent_add_controller(&self, controller: &ShortcutController) {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/sorter.rs b/gtk4/src/subclass/sorter.rs
index 1537154fc724..93bf7f855fcb 100644
--- a/gtk4/src/subclass/sorter.rs
+++ b/gtk4/src/subclass/sorter.rs
@@ -7,7 +7,7 @@ use glib::{translate::*, Object};
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Ordering, Sorter, SorterOrder};
 
-pub trait SorterImpl: SorterImplExt + ObjectImpl {
+pub trait SorterImpl: ObjectImpl + ObjectSubclass<Type: IsA<Sorter>> {
     fn compare(&self, item1: &Object, item2: &Object) -> Ordering {
         self.parent_compare(item1, item2)
     }
@@ -17,12 +17,7 @@ pub trait SorterImpl: SorterImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::SorterImplExt> Sealed for T {}
-}
-
-pub trait SorterImplExt: sealed::Sealed + ObjectSubclass {
+pub trait SorterImplExt: SorterImpl {
     fn parent_compare(&self, item1: &Object, item2: &Object) -> Ordering {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/style_context.rs b/gtk4/src/subclass/style_context.rs
index b327d9285375..b1a24ce1fa67 100644
--- a/gtk4/src/subclass/style_context.rs
+++ b/gtk4/src/subclass/style_context.rs
@@ -9,20 +9,15 @@ use crate::{ffi, prelude::*, subclass::prelude::*, StyleContext};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait StyleContextImpl: StyleContextImplExt + ObjectImpl {
+pub trait StyleContextImpl: ObjectImpl + ObjectSubclass<Type: IsA<StyleContext>> {
     fn changed(&self) {
         self.parent_changed()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::StyleContextImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait StyleContextImplExt: sealed::Sealed + ObjectSubclass {
+pub trait StyleContextImplExt: StyleContextImpl {
     fn parent_changed(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/symbolic_paintable.rs b/gtk4/src/subclass/symbolic_paintable.rs
index e3d72c7fb668..110e3c7f0904 100644
--- a/gtk4/src/subclass/symbolic_paintable.rs
+++ b/gtk4/src/subclass/symbolic_paintable.rs
@@ -8,7 +8,9 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, SymbolicPaintable};
 
-pub trait SymbolicPaintableImpl: PaintableImpl {
+pub trait SymbolicPaintableImpl:
+    PaintableImpl + ObjectSubclass<Type: IsA<SymbolicPaintable>>
+{
     fn snapshot_symbolic(
         &self,
         snapshot: &gdk::Snapshot,
@@ -20,12 +22,7 @@ pub trait SymbolicPaintableImpl: PaintableImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::SymbolicPaintableImplExt> Sealed for T {}
-}
-
-pub trait SymbolicPaintableImplExt: sealed::Sealed + ObjectSubclass {
+pub trait SymbolicPaintableImplExt: SymbolicPaintableImpl {
     fn parent_snapshot_symbolic(
         &self,
         snapshot: &gdk::Snapshot,
diff --git a/gtk4/src/subclass/text_buffer.rs b/gtk4/src/subclass/text_buffer.rs
index 4d883506aa3e..8a7f4cf23b90 100644
--- a/gtk4/src/subclass/text_buffer.rs
+++ b/gtk4/src/subclass/text_buffer.rs
@@ -9,7 +9,7 @@ use crate::{
     ffi, prelude::*, subclass::prelude::*, TextBuffer, TextChildAnchor, TextIter, TextMark, TextTag,
 };
 
-pub trait TextBufferImpl: TextBufferImplExt + ObjectImpl {
+pub trait TextBufferImpl: ObjectImpl + ObjectSubclass<Type: IsA<TextBuffer>> {
     fn apply_tag(&self, tag: &TextTag, start: &TextIter, end: &TextIter) {
         self.parent_apply_tag(tag, start, end)
     }
@@ -57,12 +57,7 @@ pub trait TextBufferImpl: TextBufferImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::TextBufferImplExt> Sealed for T {}
-}
-
-pub trait TextBufferImplExt: sealed::Sealed + ObjectSubclass {
+pub trait TextBufferImplExt: TextBufferImpl {
     fn parent_apply_tag(&self, tag: &TextTag, start: &TextIter, end: &TextIter) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/text_view.rs b/gtk4/src/subclass/text_view.rs
index 59d505bc87bb..b25738c9eac6 100644
--- a/gtk4/src/subclass/text_view.rs
+++ b/gtk4/src/subclass/text_view.rs
@@ -10,7 +10,7 @@ use crate::{
     TextIter, TextView, TextViewLayer,
 };
 
-pub trait TextViewImpl: TextViewImplExt + WidgetImpl {
+pub trait TextViewImpl: WidgetImpl + ObjectSubclass<Type: IsA<TextView>> {
     fn backspace(&self) {
         self.parent_backspace()
     }
@@ -66,12 +66,7 @@ pub trait TextViewImpl: TextViewImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::TextViewImplExt> Sealed for T {}
-}
-
-pub trait TextViewImplExt: sealed::Sealed + ObjectSubclass {
+pub trait TextViewImplExt: TextViewImpl {
     fn parent_backspace(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/toggle_button.rs b/gtk4/src/subclass/toggle_button.rs
index ad25b62d55f0..108c7e97e995 100644
--- a/gtk4/src/subclass/toggle_button.rs
+++ b/gtk4/src/subclass/toggle_button.rs
@@ -7,18 +7,13 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, ToggleButton};
 
-pub trait ToggleButtonImpl: ToggleButtonImplExt + ButtonImpl {
+pub trait ToggleButtonImpl: ButtonImpl + ObjectSubclass<Type: IsA<ToggleButton>> {
     fn toggled(&self) {
         self.parent_toggled()
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::ToggleButtonImplExt> Sealed for T {}
-}
-
-pub trait ToggleButtonImplExt: sealed::Sealed + ObjectSubclass {
+pub trait ToggleButtonImplExt: ToggleButtonImpl {
     fn parent_toggled(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/tree_drag_dest.rs b/gtk4/src/subclass/tree_drag_dest.rs
index 872c94dda14b..597d8b38a9d6 100644
--- a/gtk4/src/subclass/tree_drag_dest.rs
+++ b/gtk4/src/subclass/tree_drag_dest.rs
@@ -10,19 +10,14 @@ use crate::{ffi, prelude::*, subclass::prelude::*, TreeDragDest, TreePath};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeDragDestImpl: ObjectImpl {
+pub trait TreeDragDestImpl: ObjectImpl + ObjectSubclass<Type: IsA<TreeDragDest>> {
     fn drag_data_received(&self, dest: &TreePath, value: Value) -> bool;
     fn row_drop_possible(&self, dest: &TreePath, value: Value) -> bool;
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::TreeDragDestImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeDragDestImplExt: sealed::Sealed + ObjectSubclass {
+pub trait TreeDragDestImplExt: TreeDragDestImpl {
     fn parent_drag_data_received(&self, dest: &TreePath, value: Value) -> bool {
         unsafe {
             let type_data = Self::type_data();
diff --git a/gtk4/src/subclass/tree_drag_source.rs b/gtk4/src/subclass/tree_drag_source.rs
index 162bf6c73825..07b754fd2d5e 100644
--- a/gtk4/src/subclass/tree_drag_source.rs
+++ b/gtk4/src/subclass/tree_drag_source.rs
@@ -10,7 +10,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, TreeDragSource, TreePath};
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeDragSourceImpl: ObjectImpl {
+pub trait TreeDragSourceImpl: ObjectImpl + ObjectSubclass<Type: IsA<TreeDragSource>> {
     fn row_draggable(&self, path: &TreePath) -> bool {
         self.parent_row_draggable(path)
     }
@@ -18,14 +18,9 @@ pub trait TreeDragSourceImpl: ObjectImpl {
     fn drag_data_delete(&self, path: &TreePath) -> bool;
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::TreeDragSourceImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeDragSourceImplExt: sealed::Sealed + ObjectSubclass {
+pub trait TreeDragSourceImplExt: TreeDragSourceImpl {
     // Returns true if the row can be dragged
     fn parent_row_draggable(&self, path: &TreePath) -> bool {
         unsafe {
diff --git a/gtk4/src/subclass/tree_model_filter.rs b/gtk4/src/subclass/tree_model_filter.rs
index 366994170fc6..a2b1d6d18190 100644
--- a/gtk4/src/subclass/tree_model_filter.rs
+++ b/gtk4/src/subclass/tree_model_filter.rs
@@ -9,7 +9,7 @@ use crate::{ffi, prelude::*, subclass::prelude::*, TreeIter, TreeModel, TreeMode
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeModelFilterImpl: TreeModelFilterImplExt + ObjectImpl {
+pub trait TreeModelFilterImpl: ObjectImpl + ObjectSubclass<Type: IsA<TreeModelFilter>> {
     fn visible<M: IsA<TreeModel>>(&self, child_model: &M, iter: &TreeIter) -> bool {
         self.parent_visible(child_model, iter)
     }
@@ -25,14 +25,9 @@ pub trait TreeModelFilterImpl: TreeModelFilterImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::TreeModelFilterImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeModelFilterImplExt: sealed::Sealed + ObjectSubclass {
+pub trait TreeModelFilterImplExt: TreeModelFilterImpl {
     // Whether the row indicated by iter is visible
     fn parent_visible<M: IsA<TreeModel>>(&self, child_model: &M, iter: &TreeIter) -> bool {
         unsafe {
diff --git a/gtk4/src/subclass/tree_view.rs b/gtk4/src/subclass/tree_view.rs
index 1acf7f417a28..e05cfbbd1334 100644
--- a/gtk4/src/subclass/tree_view.rs
+++ b/gtk4/src/subclass/tree_view.rs
@@ -12,7 +12,7 @@ use crate::{
 
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeViewImpl: TreeViewImplExt + WidgetImpl {
+pub trait TreeViewImpl: WidgetImpl + ObjectSubclass<Type: IsA<TreeView>> {
     fn columns_changed(&self) {
         self.parent_columns_changed()
     }
@@ -74,14 +74,9 @@ pub trait TreeViewImpl: TreeViewImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::TreeViewImplExt> Sealed for T {}
-}
-
 #[cfg_attr(feature = "v4_10", deprecated = "Since 4.10")]
 #[allow(deprecated)]
-pub trait TreeViewImplExt: sealed::Sealed + ObjectSubclass {
+pub trait TreeViewImplExt: TreeViewImpl {
     fn parent_columns_changed(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/widget.rs b/gtk4/src/subclass/widget.rs
index a771c73aeac5..b0b7cb3ee190 100644
--- a/gtk4/src/subclass/widget.rs
+++ b/gtk4/src/subclass/widget.rs
@@ -104,7 +104,7 @@ impl Iterator for WidgetActionIter {
 
 impl std::iter::FusedIterator for WidgetActionIter {}
 
-pub trait WidgetImpl: WidgetImplExt + ObjectImpl {
+pub trait WidgetImpl: ObjectImpl + ObjectSubclass<Type: IsA<Widget>> {
     fn compute_expand(&self, hexpand: &mut bool, vexpand: &mut bool) {
         self.parent_compute_expand(hexpand, vexpand)
     }
@@ -207,12 +207,7 @@ pub trait WidgetImpl: WidgetImplExt + ObjectImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::WidgetImplExt> Sealed for T {}
-}
-
-pub trait WidgetImplExt: sealed::Sealed + ObjectSubclass {
+pub trait WidgetImplExt: WidgetImpl {
     fn parent_compute_expand(&self, hexpand: &mut bool, vexpand: &mut bool) {
         unsafe {
             let data = Self::type_data();
@@ -1428,17 +1423,15 @@ pub trait CompositeTemplateInitializingExt {
     fn init_template(&self);
 }
 
-impl<T> CompositeTemplateInitializingExt for glib::subclass::InitializingObject<T>
-where
-    T: WidgetImpl + CompositeTemplate,
-    <T as ObjectSubclass>::Type: IsA<Widget>,
+impl<T: WidgetImpl + CompositeTemplate> CompositeTemplateInitializingExt
+    for glib::subclass::InitializingObject<T>
 {
     fn init_template(&self) {
         unsafe {
             let widget = self
                 .as_ref()
                 .unsafe_cast_ref::<<T as ObjectSubclass>::Type>();
-            ffi::gtk_widget_init_template(widget.as_ref().to_glib_none().0);
+            ffi::gtk_widget_init_template(AsRef::<Widget>::as_ref(widget).to_glib_none().0);
 
             <T as CompositeTemplate>::check_template_children(widget);
         }
@@ -1451,11 +1444,7 @@ pub trait CompositeTemplateDisposeExt {
     fn dispose_template(&self);
 }
 
-impl<T> CompositeTemplateDisposeExt for T
-where
-    T: WidgetImpl + CompositeTemplate,
-    <T as ObjectSubclass>::Type: IsA<Widget>,
-{
+impl<T: WidgetImpl + CompositeTemplate> CompositeTemplateDisposeExt for T {
     #[cfg(feature = "v4_8")]
     #[cfg_attr(docsrs, doc(cfg(feature = "v4_8")))]
     fn dispose_template(&self) {
diff --git a/gtk4/src/subclass/window.rs b/gtk4/src/subclass/window.rs
index 76b2636a2ad5..ba0cf77a3886 100644
--- a/gtk4/src/subclass/window.rs
+++ b/gtk4/src/subclass/window.rs
@@ -7,7 +7,7 @@ use glib::translate::*;
 
 use crate::{ffi, prelude::*, subclass::prelude::*, Window};
 
-pub trait WindowImpl: WindowImplExt + WidgetImpl {
+pub trait WindowImpl: WidgetImpl + ObjectSubclass<Type: IsA<Window>> {
     fn activate_focus(&self) {
         self.parent_activate_focus()
     }
@@ -29,12 +29,7 @@ pub trait WindowImpl: WindowImplExt + WidgetImpl {
     }
 }
 
-mod sealed {
-    pub trait Sealed {}
-    impl<T: super::WindowImplExt> Sealed for T {}
-}
-
-pub trait WindowImplExt: sealed::Sealed + ObjectSubclass {
+pub trait WindowImplExt: WindowImpl {
     fn parent_activate_focus(&self) {
         unsafe {
             let data = Self::type_data();
diff --git a/gtk4/src/subclass/window_group.rs b/gtk4/src/subclass/window_group.rs
index 0ef941991362..97cea079e9dc 100644
--- a/gtk4/src/subclass/window_group.rs
+++ b/gtk4/src/subclass/window_group.rs
@@ -3,8 +3,8 @@
 // rustdoc-stripper-ignore-next
 //! Traits intended for subclassing [`WindowGroup`](crate::WindowGroup).
 
-use crate::{subclass::prelude::*, WindowGroup};
+use crate::{prelude::*, subclass::prelude::*, WindowGroup};
 
-pub trait WindowGroupImpl: ObjectImpl {}
+pub trait WindowGroupImpl: ObjectImpl + ObjectSubclass<Type: IsA<WindowGroup>> {}
 
 unsafe impl<T: WindowGroupImpl> IsSubclassable<T> for WindowGroup {}