diff --git a/python/sglang/srt/sampling/sampling_params.py b/python/sglang/srt/sampling/sampling_params.py
index a7f4c664f..463c6e17f 100644
--- a/python/sglang/srt/sampling/sampling_params.py
+++ b/python/sglang/srt/sampling/sampling_params.py
@@ -68,7 +68,8 @@ class SamplingParams:
         self.max_new_tokens = max_new_tokens
         self.stop_strs = stop
         if stop_token_ids:
-            self.stop_token_ids = set(stop_token_ids)
+            filtered = {int(t) for t in stop_token_ids if t is not None}
+            self.stop_token_ids = filtered or None
         else:
             self.stop_token_ids = None
         self.stop_regex_strs = stop_regex