diff --git a/autogen/oai/client.py b/autogen/oai/client.py
index 833cc7772196..481e55728c54 100644
--- a/autogen/oai/client.py
+++ b/autogen/oai/client.py
@@ -1069,7 +1069,7 @@ def extract_text_or_completion_object(
 
     def _throttle_api_calls(self, idx: int) -> None:
         """Rate limit api calls."""
-        if self._rate_limiters[idx]:
+        if idx < len(self._rate_limiters) and self._rate_limiters[idx]:
             limiter = self._rate_limiters[idx]
 
             assert limiter is not None