diff --git a/src/backend/postgres/types.rs b/src/backend/postgres/types.rs
index db5a43b7..3ec126d5 100644
--- a/src/backend/postgres/types.rs
+++ b/src/backend/postgres/types.rs
@@ -88,22 +88,27 @@ impl PostgresQueryBuilder {
 
     fn prepare_alter_type_opt(&self, opt: &TypeAlterOpt, sql: &mut dyn SqlWriter) {
         match opt {
-            TypeAlterOpt::Add(value, placement) => {
+            TypeAlterOpt::Add {
+                value,
+                placement,
+                if_not_exists,
+            } => {
                 write!(sql, " ADD VALUE ").unwrap();
-                match placement {
-                    Some(add_option) => match add_option {
+                if *if_not_exists {
+                    write!(sql, "IF NOT EXISTS ").unwrap();
+                }
+                self.prepare_value(&value.to_string().into(), sql);
+                if let Some(add_option) = placement {
+                    match add_option {
                         TypeAlterAddOpt::Before(before_value) => {
-                            self.prepare_value(&value.to_string().into(), sql);
                             write!(sql, " BEFORE ").unwrap();
                             self.prepare_value(&before_value.to_string().into(), sql);
                         }
                         TypeAlterAddOpt::After(after_value) => {
-                            self.prepare_value(&value.to_string().into(), sql);
                             write!(sql, " AFTER ").unwrap();
                             self.prepare_value(&after_value.to_string().into(), sql);
                         }
-                    },
-                    None => self.prepare_value(&value.to_string().into(), sql),
+                    }
                 }
             }
             TypeAlterOpt::Rename(new_name) => {
diff --git a/src/extension/postgres/types.rs b/src/extension/postgres/types.rs
index 3aff184d..29bda947 100644
--- a/src/extension/postgres/types.rs
+++ b/src/extension/postgres/types.rs
@@ -88,7 +88,11 @@ pub enum TypeDropOpt {
 
 #[derive(Debug, Clone)]
 pub enum TypeAlterOpt {
-    Add(DynIden, Option<TypeAlterAddOpt>),
+    Add {
+        value: DynIden,
+        placement: Option<TypeAlterAddOpt>,
+        if_not_exists: bool,
+    },
     Rename(DynIden),
     RenameValue(DynIden, DynIden),
 }
@@ -361,7 +365,11 @@ impl TypeAlterStatement {
     where
         T: IntoIden,
     {
-        self.alter_option(TypeAlterOpt::Add(value.into_iden(), None))
+        self.alter_option(TypeAlterOpt::Add {
+            value: value.into_iden(),
+            placement: None,
+            if_not_exists: false,
+        })
     }
 
     /// Add a enum value before an existing value
@@ -398,6 +406,13 @@ impl TypeAlterStatement {
         self
     }
 
+    pub fn if_not_exists(mut self) -> Self {
+        if let Some(option) = self.option {
+            self.option = Some(option.if_not_exists());
+        }
+        self
+    }
+
     pub fn rename_to<T>(self, name: T) -> Self
     where
         T: IntoIden,
@@ -442,9 +457,15 @@ impl TypeAlterOpt {
         T: IntoIden,
     {
         match self {
-            TypeAlterOpt::Add(iden, _) => {
-                Self::Add(iden, Some(TypeAlterAddOpt::Before(value.into_iden())))
-            }
+            TypeAlterOpt::Add {
+                value: iden,
+                if_not_exists,
+                ..
+            } => Self::Add {
+                value: iden,
+                if_not_exists,
+                placement: Some(TypeAlterAddOpt::Before(value.into_iden())),
+            },
             _ => self,
         }
     }
@@ -455,9 +476,29 @@ impl TypeAlterOpt {
         T: IntoIden,
     {
         match self {
-            TypeAlterOpt::Add(iden, _) => {
-                Self::Add(iden, Some(TypeAlterAddOpt::After(value.into_iden())))
-            }
+            TypeAlterOpt::Add {
+                value: iden,
+                if_not_exists,
+                ..
+            } => Self::Add {
+                value: iden,
+                if_not_exists,
+                placement: Some(TypeAlterAddOpt::After(value.into_iden())),
+            },
+            _ => self,
+        }
+    }
+
+    /// Changes only `ADD VALUE x` options into `ADD VALUE IF NOT EXISTS x` options, does nothing otherwise
+    pub fn if_not_exists(self) -> Self {
+        match self {
+            TypeAlterOpt::Add {
+                value, placement, ..
+            } => Self::Add {
+                value,
+                placement,
+                if_not_exists: true,
+            },
             _ => self,
         }
     }