diff --git a/python/packages/autogen-ext/src/autogen_ext/models/openai/config/__init__.py b/python/packages/autogen-ext/src/autogen_ext/models/openai/config/__init__.py
index a6b484780212..de27637c4663 100644
--- a/python/packages/autogen-ext/src/autogen_ext/models/openai/config/__init__.py
+++ b/python/packages/autogen-ext/src/autogen_ext/models/openai/config/__init__.py
@@ -74,7 +74,7 @@ class BaseOpenAIClientConfigurationConfigModel(CreateArgumentsConfigModel):
     max_retries: int | None = None
     model_capabilities: ModelCapabilities | None = None  # type: ignore
     model_info: ModelInfo | None = None
-
+    default_header: Dict[str, str] | None = None
 
 # See OpenAI docs for explanation of these parameters
 class OpenAIClientConfigurationConfigModel(BaseOpenAIClientConfigurationConfigModel):