diff --git a/python/sglang/srt/entrypoints/http_server.py b/python/sglang/srt/entrypoints/http_server.py
index 147ab4131..1064d2dbf 100644
--- a/python/sglang/srt/entrypoints/http_server.py
+++ b/python/sglang/srt/entrypoints/http_server.py
@@ -675,6 +675,8 @@ async def vertex_generate(vertex_req: VertexGenerateReqInput, raw_request: Reque
         **(vertex_req.parameters or {}),
     )
     ret = await generate_request(req, raw_request)
+    if isinstance(ret, Response):
+        return ret
     return ORJSONResponse({"predictions": ret})
 
 
diff --git a/test/srt/test_vertex_endpoint.py b/test/srt/test_vertex_endpoint.py
index a899d6251..42e48cb1b 100644
--- a/test/srt/test_vertex_endpoint.py
+++ b/test/srt/test_vertex_endpoint.py
@@ -3,6 +3,7 @@ python3 -m unittest test_vertex_endpoint.TestVertexEndpoint.test_vertex_generate
 """
 
 import unittest
+from http import HTTPStatus
 
 import requests
 
@@ -49,6 +50,15 @@ class TestVertexEndpoint(CustomTestCase):
         for parameters in [None, {"sampling_params": {"max_new_tokens": 4}}]:
             self.run_generate(parameters)
 
+    def test_vertex_generate_fail(self):
+        data = {
+            "instances": [
+                {"prompt": "The capital of France is"},
+            ],
+        }
+        response = requests.post(self.base_url + "/vertex_generate", json=data)
+        assert response.status_code == HTTPStatus.BAD_REQUEST
+
 
 if __name__ == "__main__":
     unittest.main()