diff --git a/tests/test_union_body_discriminator_annotated.py b/tests/test_union_body_discriminator_annotated.py
index 503b7978d..14145e6f6 100644
--- a/tests/test_union_body_discriminator_annotated.py
+++ b/tests/test_union_body_discriminator_annotated.py
@@ -26,9 +26,8 @@ def client_fixture() -> TestClient:
         barks: float
 
     def get_pet_type(v):
-        if isinstance(v, dict):
-            return v.get("pet_type", "")
-        return getattr(v, "pet_type", "")
+        assert isinstance(v, dict)
+        return v.get("pet_type", "")
 
     Pet = Annotated[
         Union[Annotated[Cat, Tag("cat")], Annotated[Dog, Tag("dog")]],