diff --git a/gdk4/src/dmabuf_texture_builder.rs b/gdk4/src/dmabuf_texture_builder.rs
index 1a81f3874220..2e3c7eed5c3b 100644
--- a/gdk4/src/dmabuf_texture_builder.rs
+++ b/gdk4/src/dmabuf_texture_builder.rs
@@ -34,12 +34,14 @@ impl DmabufTextureBuilder {
     #[doc(alias = "gdk_dmabuf_texture_builder_build")]
     #[must_use = "The builder must be built to be used"]
     #[allow(clippy::missing_safety_doc)]
-    pub unsafe fn build_with_release_func<F: FnOnce() + 'static>(
+    pub unsafe fn build_with_release_func<F: FnOnce() + Send + 'static>(
         self,
         release_func: F,
     ) -> Result<Texture, glib::Error> {
         let mut error = std::ptr::null_mut();
-        unsafe extern "C" fn destroy_closure<F: FnOnce() + 'static>(func: glib::ffi::gpointer) {
+        unsafe extern "C" fn destroy_closure<F: FnOnce() + Send + 'static>(
+            func: glib::ffi::gpointer,
+        ) {
             let released_func = Box::<F>::from_raw(func as *mut _);
             released_func();
         }
diff --git a/gdk4/src/gl_texture_builder.rs b/gdk4/src/gl_texture_builder.rs
index 534385b64ec2..12baf089eac3 100644
--- a/gdk4/src/gl_texture_builder.rs
+++ b/gdk4/src/gl_texture_builder.rs
@@ -25,8 +25,13 @@ impl GLTextureBuilder {
     #[doc(alias = "gdk_gl_texture_builder_build")]
     #[must_use = "The builder must be built to be used"]
     #[allow(clippy::missing_safety_doc)]
-    pub unsafe fn build_with_release_func<F: FnOnce() + 'static>(self, release_func: F) -> Texture {
-        unsafe extern "C" fn destroy_closure<F: FnOnce() + 'static>(func: glib::ffi::gpointer) {
+    pub unsafe fn build_with_release_func<F: FnOnce() + Send + 'static>(
+        self,
+        release_func: F,
+    ) -> Texture {
+        unsafe extern "C" fn destroy_closure<F: FnOnce() + Send + 'static>(
+            func: glib::ffi::gpointer,
+        ) {
             let released_func = Box::<F>::from_raw(func as *mut _);
             released_func();
         }