diff --git a/libs/partners/prompty/tests/unit_tests/fake_chat_model.py b/libs/partners/prompty/tests/unit_tests/fake_chat_model.py
index a39f401e64349..0bfc795f7c656 100644
--- a/libs/partners/prompty/tests/unit_tests/fake_chat_model.py
+++ b/libs/partners/prompty/tests/unit_tests/fake_chat_model.py
@@ -21,7 +21,7 @@ def _call(
         run_manager: Optional[CallbackManagerForLLMRun] = None,
         **kwargs: Any,
     ) -> str:
-        return json.dumps([message.dict() for message in messages])
+        return json.dumps([message.model_dump() for message in messages])
 
     async def _agenerate(
         self,