diff --git a/python/sglang/srt/entrypoints/openai/serving_chat.py b/python/sglang/srt/entrypoints/openai/serving_chat.py
index 67cfef0a9..61d467cb8 100644
--- a/python/sglang/srt/entrypoints/openai/serving_chat.py
+++ b/python/sglang/srt/entrypoints/openai/serving_chat.py
@@ -1359,7 +1359,8 @@ class OpenAIServingChat(OpenAIServingBase):
                     arguments=call_item.parameters,
                 ),
             )
-
+            if tool_call_id is None:
+                tool_call.type = None
             choice_data = ChatCompletionResponseStreamChoice(
                 index=index,
                 delta=DeltaMessage(tool_calls=[tool_call]),