diff --git a/litellm/llms/anthropic/chat/transformation.py b/litellm/llms/anthropic/chat/transformation.py
index aff70a6e628..1a77c453f40 100644
--- a/litellm/llms/anthropic/chat/transformation.py
+++ b/litellm/llms/anthropic/chat/transformation.py
@@ -387,7 +387,7 @@ class AnthropicConfig(BaseConfig):
             _input_schema["additionalProperties"] = True
             _input_schema["properties"] = {}
         else:
-            _input_schema.update(json_schema)
+            _input_schema.update(cast(AnthropicInputSchema, json_schema))
 
         _tool = AnthropicMessagesTool(
             name=RESPONSE_FORMAT_TOOL_NAME, input_schema=_input_schema