diff --git a/src/ragas/llms/base.py b/src/ragas/llms/base.py
index ecbf6279e..a18fd55e9 100644
--- a/src/ragas/llms/base.py
+++ b/src/ragas/llms/base.py
@@ -157,7 +157,7 @@ def is_finished(self, response: LLMResult) -> bool:
 
             # if generation_info is empty, we parse the response_metadata
             # this is less reliable
-            elif t.cast(ChatGeneration, resp).message is not None:
+            elif isinstance(resp, ChatGeneration) and t.cast(ChatGeneration, resp).message is not None:
                 resp_message: BaseMessage = t.cast(ChatGeneration, resp).message
                 if resp_message.response_metadata.get("finish_reason") is not None:
                     is_finished_list.append(