diff --git a/python/packages/autogen-core/src/autogen_core/models/_types.py b/python/packages/autogen-core/src/autogen_core/models/_types.py
index fb118562e4d3..a3d6af1edde4 100644
--- a/python/packages/autogen-core/src/autogen_core/models/_types.py
+++ b/python/packages/autogen-core/src/autogen_core/models/_types.py
@@ -52,7 +52,7 @@ class RequestUsage:
     completion_tokens: int
 
 
-FinishReasons = Literal["stop", "length", "function_calls", "content_filter"]
+FinishReasons = Literal["stop", "length", "function_calls", "content_filter", "unknown"]
 
 
 @dataclass