diff --git a/litellm/responses/litellm_completion_transformation/transformation.py b/litellm/responses/litellm_completion_transformation/transformation.py
index 5d5e305c7e6..7096c1cdf45 100644
--- a/litellm/responses/litellm_completion_transformation/transformation.py
+++ b/litellm/responses/litellm_completion_transformation/transformation.py
@@ -32,6 +32,7 @@ from litellm.types.llms.openai import (
     OpenAIWebSearchOptions,
     OpenAIWebSearchUserLocation,
     OutputTokensDetails,
+    Reasoning,
     ResponseAPIUsage,
     ResponsesAPIOptionalRequestParams,
     ResponsesAPIResponse,
@@ -181,7 +182,7 @@ class LiteLLMCompletionResponsesConfig:
             )
 
         # Extract reasoning_effort from reasoning parameter
-        reasoning_effort = None
+        reasoning_effort: Optional[Union[Reasoning, str]] = None
         reasoning_param = responses_api_request.get("reasoning")
         if reasoning_param:
             if isinstance(reasoning_param, dict):