diff --git a/litellm/llms/openai/chat/gpt_5_transformation.py b/litellm/llms/openai/chat/gpt_5_transformation.py
index bd726e7933..1a976beac8 100644
--- a/litellm/llms/openai/chat/gpt_5_transformation.py
+++ b/litellm/llms/openai/chat/gpt_5_transformation.py
@@ -224,6 +224,7 @@ class OpenAIGPT5Config(OpenAIGPTConfig):
             if not self._supports_reasoning_effort_level(model, effective_effort):
                 if litellm.drop_params or drop_params:
                     non_default_params.pop("reasoning_effort", None)
+                    optional_params.pop("reasoning_effort", None)
                 else:
                     raise litellm.utils.UnsupportedParamsError(
                         message=(