diff --git a/lmdeploy/serve/openai/api_server.py b/lmdeploy/serve/openai/api_server.py
index 4ec2d58636..28096af9b6 100644
--- a/lmdeploy/serve/openai/api_server.py
+++ b/lmdeploy/serve/openai/api_server.py
@@ -57,9 +57,10 @@ def create_error_response(status: HTTPStatus, message: str):
         status (HTTPStatus): HTTP status codes and reason phrases
         message (str): error message
     """
-    return JSONResponse(ErrorResponse(message=message,
-                                      type='invalid_request_error').dict(),
-                        status_code=status.value)
+    return JSONResponse(
+        ErrorResponse(message=message,
+                      type='invalid_request_error',
+                      code=status.value).dict())
 
 
 async def check_request(request) -> Optional[JSONResponse]:
@@ -117,7 +118,7 @@ async def chat_completions_v1(request: ChatCompletionRequest,
     result_generator = VariableInterface.async_engine.generate_openai(
         request.messages,
         instance_id,
-        request.stream,
+        True,  # always use stream to enable batching
         request.renew_session,
         request_output_len=request.max_tokens if request.max_tokens else 512,
         stop=request.stop,
@@ -130,7 +131,7 @@ async def abort_request() -> None:
         async for _ in VariableInterface.async_engine.generate_openai(
                 request.messages,
                 instance_id,
-                request.stream,
+                True,
                 request.renew_session,
                 stop=True):
             pass
@@ -188,6 +189,7 @@ async def completion_stream_generator() -> AsyncGenerator[str, None]:
 
     # Non-streaming response
     final_res = None
+    text = ''
     async for res in result_generator:
         if await raw_request.is_disconnected():
             # Abort the request if the client disconnects.
@@ -195,11 +197,12 @@ async def completion_stream_generator() -> AsyncGenerator[str, None]:
             return create_error_response(HTTPStatus.BAD_REQUEST,
                                          'Client disconnected')
         final_res = res
+        text += res.response
     assert final_res is not None
     choices = []
     choice_data = ChatCompletionResponseChoice(
         index=0,
-        message=ChatMessage(role='assistant', content=final_res.response),
+        message=ChatMessage(role='assistant', content=text),
         finish_reason=final_res.finish_reason,
     )
     choices.append(choice_data)
@@ -308,7 +311,7 @@ async def stream_results() -> AsyncGenerator[bytes, None]:
         finish_reason = None
         async for out in generation:
             text += out.response
-            tokens += out.generate_token_len
+            tokens = out.generate_token_len
             finish_reason = out.finish_reason
         ret = {'text': text, 'tokens': tokens, 'finish_reason': finish_reason}
         return JSONResponse(ret)