diff --git a/python/sglang/srt/entrypoints/openai/protocol.py b/python/sglang/srt/entrypoints/openai/protocol.py
index d23366372..f142d198d 100644
--- a/python/sglang/srt/entrypoints/openai/protocol.py
+++ b/python/sglang/srt/entrypoints/openai/protocol.py
@@ -1320,7 +1320,7 @@ class ResponseTool(BaseModel):
     tools: Optional[List[Dict[str, Any]]] = None
 
     @model_validator(mode="after")
-    def validate_function_tool(self) -> "ResponseTool":
+    def validate_function_tool(self) -> ResponseTool:
         if self.type == "function" and not self.name:
             raise ValueError("Function tools must include a name.")
         return self