diff --git a/langchain/llms/cohere.py b/langchain/llms/cohere.py
index 5d642038198..76ecc7cdfaa 100644
--- a/langchain/llms/cohere.py
+++ b/langchain/llms/cohere.py
@@ -22,7 +22,7 @@ class Cohere(BaseModel, LLM):
     """
 
     client: Any  #: :meta private:
-    model: str = None
+    model: Optional[str] = None
     """Model name to use."""
 
     max_tokens: int = 256