diff --git a/apps/setting/models_provider/impl/base_chat_open_ai.py b/apps/setting/models_provider/impl/base_chat_open_ai.py
index e0d0e762e..c96bfacf2 100644
--- a/apps/setting/models_provider/impl/base_chat_open_ai.py
+++ b/apps/setting/models_provider/impl/base_chat_open_ai.py
@@ -24,10 +24,11 @@ def _convert_delta_to_message_chunk(
         _dict: Mapping[str, Any], default_class: type[BaseMessageChunk]
 ) -> BaseMessageChunk:
     id_ = _dict.get("id")
-    reasoning_content = cast(str, _dict.get("reasoning_content") or "")
     role = cast(str, _dict.get("role"))
     content = cast(str, _dict.get("content") or "")
-    additional_kwargs: dict = {'reasoning_content': reasoning_content}
+    additional_kwargs: dict = {}
+    if 'reasoning_content' in _dict:
+        additional_kwargs['reasoning_content'] = _dict.get('reasoning_content')
     if _dict.get("function_call"):
         function_call = dict(_dict["function_call"])
         if "name" in function_call and function_call["name"] is None: