diff --git a/python/llm/src/ipex_llm/serving/fastchat/ipex_llm_worker.py b/python/llm/src/ipex_llm/serving/fastchat/ipex_llm_worker.py
index b357c8d3..9fbe1cb7 100644
--- a/python/llm/src/ipex_llm/serving/fastchat/ipex_llm_worker.py
+++ b/python/llm/src/ipex_llm/serving/fastchat/ipex_llm_worker.py
@@ -100,7 +100,9 @@ class BigDLLLMWorker(BaseModelWorker):
         temperature = float(params.get("temperature", 1.0))
         repetition_penalty = float(params.get("repetition_penalty", 1.0))
         top_p = float(params.get("top_p", 1.0))
-        top_k = int(params.get("top_k", 0))  # 0 means disable
+        top_k = int(params.get("top_k", 1))
+        if top_k == -1:
+            top_k = 1
         max_new_tokens = int(params.get("max_new_tokens", 256))
         echo = bool(params.get("echo", True))
         stop_str = params.get("stop", None)