diff --git a/crates/cairo-lang-semantic/src/expr/inference.rs b/crates/cairo-lang-semantic/src/expr/inference.rs
index 1ee0de9fc3b..7319222fb9f 100644
--- a/crates/cairo-lang-semantic/src/expr/inference.rs
+++ b/crates/cairo-lang-semantic/src/expr/inference.rs
@@ -1230,15 +1230,9 @@ impl SemanticRewriter<TypeLongId, NoError> for Inference<'_> {
                 let impl_id = impl_type_id.impl_id();
                 let trait_ty = impl_type_id.ty();
                 return Ok(match impl_id.lookup_intern(self.db) {
-                    ImplLongId::GenericParameter(_) | ImplLongId::SelfImpl(_) => {
-                        impl_type_id_rewrite_result
-                    }
-                    ImplLongId::ImplImpl(impl_impl) => {
-                        // The grand parent impl must be var free since we are rewriting the parent,
-                        // and the parent is not var.
-                        assert!(impl_impl.impl_id().is_var_free(self.db));
-                        impl_type_id_rewrite_result
-                    }
+                    ImplLongId::GenericParameter(_)
+                    | ImplLongId::SelfImpl(_)
+                    | ImplLongId::ImplImpl(_) => impl_type_id_rewrite_result,
                     ImplLongId::Concrete(_) => {
                         if let Ok(ty) = self.db.impl_type_concrete_implized(ImplTypeId::new(
                             impl_id, trait_ty, self.db,
diff --git a/crates/cairo-lang-semantic/src/items/tests/trait_impl b/crates/cairo-lang-semantic/src/items/tests/trait_impl
index c43922036eb..f5b133ceba3 100644
--- a/crates/cairo-lang-semantic/src/items/tests/trait_impl
+++ b/crates/cairo-lang-semantic/src/items/tests/trait_impl
@@ -1367,3 +1367,64 @@ error: Trait has no implementation in context: core::metaprogramming::TypeEqual:
  --> lib.cairo:31:11
     1_u64.foo(1_u32);
           ^^^
+
+//! > ==========================================================================
+
+//! > Trait default implementation with recursive types.
+
+//! > test_runner_name
+test_function_diagnostics(expect_diagnostics: true)
+
+//! > function
+fn foo() {
+    // TODO(orizi): Remove this diagnostic.
+    mix(1_u64.into_inner(), 1_u32.into_inner());
+}
+
+//! > function_name
+foo
+
+//! > module_code
+trait Outer<T> {
+    type Inner;
+    impl Impl: Inner<Self::Inner>;
+    fn into_inner(self: T) -> Self::Inner;
+}
+
+trait Inner<T> {
+    type InnerMost;
+}
+
+fn mix<
+    T,
+    U,
+    impl InnerT: Inner<T>,
+    impl OuterU: Outer<U>,
+    +core::metaprogramming::TypeEqual<InnerT::InnerMost, OuterU::Impl::InnerMost>,
+>(
+    lhs: T, rhs: U,
+) {}
+
+impl OuterU32 of Outer<u32> {
+    type Inner = u64;
+    fn into_inner(self: u32) -> u64 {
+        self.into()
+    }
+}
+
+impl OuterU64 of Outer<u64> {
+    type Inner = u64;
+    fn into_inner(self: u64) -> u64 {
+        self
+    }
+}
+
+impl InnerImpl of Inner<u64> {
+    type InnerMost = u128;
+}
+
+//! > expected_diagnostics
+error: Impl mismatch: `Outer::Impl` and `test::InnerImpl`.
+ --> lib.cairo:40:5
+    mix(1_u64.into_inner(), 1_u32.into_inner());
+    ^^^