diff --git a/crates/syntax/rust.ungram b/crates/syntax/rust.ungram
index 19e642968c..62aa478399 100644
--- a/crates/syntax/rust.ungram
+++ b/crates/syntax/rust.ungram
@@ -51,7 +51,7 @@ TypeArg =
   Type
 
 AssocTypeArg =
-  NameRef GenericParamList? (':' TypeBoundList | '=' Type)
+  NameRef GenericParamList? (':' TypeBoundList | ('=' Type | ConstArg))
 
 LifetimeArg =
   Lifetime
diff --git a/crates/syntax/src/ast/generated/nodes.rs b/crates/syntax/src/ast/generated/nodes.rs
index 92d793e0fd..cf90ba64cf 100644
--- a/crates/syntax/src/ast/generated/nodes.rs
+++ b/crates/syntax/src/ast/generated/nodes.rs
@@ -123,6 +123,7 @@ impl AssocTypeArg {
     pub fn generic_param_list(&self) -> Option<GenericParamList> { support::child(&self.syntax) }
     pub fn eq_token(&self) -> Option<SyntaxToken> { support::token(&self.syntax, T![=]) }
     pub fn ty(&self) -> Option<Type> { support::child(&self.syntax) }
+    pub fn const_arg(&self) -> Option<ConstArg> { support::child(&self.syntax) }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]