diff --git a/crates/ty_python_semantic/src/types/generics.rs b/crates/ty_python_semantic/src/types/generics.rs
index 8ae3f0f434..df9aa8d7f4 100644
--- a/crates/ty_python_semantic/src/types/generics.rs
+++ b/crates/ty_python_semantic/src/types/generics.rs
@@ -1677,22 +1677,38 @@ impl<'db> SpecializationBuilder<'db> {
             }
 
             (Type::Callable(formal_callable), _) => {
-                if let Some(actual_callable) = actual
+                let Some(actual_callable) = actual
                     .try_upcast_to_callable(self.db)
                     .and_then(CallableTypes::exactly_one)
-                {
-                    for formal_signature in &formal_callable.signatures(self.db).overloads {
-                        for actual_signature in &actual_callable.signatures(self.db).overloads {
-                            if let Some(formal_return_ty) = formal_signature.return_ty
-                                && let Some(actual_return_ty) = actual_signature.return_ty
-                            {
-                                self.infer_map_impl(
-                                    formal_return_ty,
-                                    actual_return_ty,
-                                    polarity,
-                                    &mut f,
-                                )?;
-                            }
+                else {
+                    return Ok(());
+                };
+
+                let [formal_signature] = formal_callable.signatures(self.db).overloads.as_slice()
+                else {
+                    return Ok(());
+                };
+                let [actual_signature] = actual_callable.signatures(self.db).overloads.as_slice()
+                else {
+                    return Ok(());
+                };
+
+                let when = formal_signature.when_constraint_set_assignable_to(
+                    self.db,
+                    actual_signature,
+                    self.inferable,
+                );
+                for formal_signature in &formal_callable.signatures(self.db).overloads {
+                    for actual_signature in &actual_callable.signatures(self.db).overloads {
+                        if let Some(formal_return_ty) = formal_signature.return_ty
+                            && let Some(actual_return_ty) = actual_signature.return_ty
+                        {
+                            self.infer_map_impl(
+                                formal_return_ty,
+                                actual_return_ty,
+                                polarity,
+                                &mut f,
+                            )?;
                         }
                     }
                 }
diff --git a/crates/ty_python_semantic/src/types/signatures.rs b/crates/ty_python_semantic/src/types/signatures.rs
index ebe2945693..5abc9ebe38 100644
--- a/crates/ty_python_semantic/src/types/signatures.rs
+++ b/crates/ty_python_semantic/src/types/signatures.rs
@@ -839,6 +839,22 @@ impl<'db> Signature<'db> {
         result
     }
 
+    pub(crate) fn when_constraint_set_assignable_to(
+        &self,
+        db: &'db dyn Db,
+        other: &Signature<'db>,
+        inferable: InferableTypeVars<'_, 'db>,
+    ) -> ConstraintSet<'db> {
+        self.has_relation_to_impl(
+            db,
+            other,
+            inferable,
+            TypeRelation::ConstraintSetAssignability,
+            &HasRelationToVisitor::default(),
+            &IsDisjointVisitor::default(),
+        )
+    }
+
     /// Implementation of subtyping and assignability for signature.
     fn has_relation_to_impl(
         &self,
@@ -1175,7 +1191,9 @@ impl<'db> Signature<'db> {
                             break;
                         }
 
-                        _ => return ConstraintSet::from(false),
+                        _ => {
+                            return ConstraintSet::from(false);
+                        }
                     }
                 }
             }