diff --git a/extensions/openai/typing.py b/extensions/openai/typing.py
index af7b094f..5e26ce0c 100644
--- a/extensions/openai/typing.py
+++ b/extensions/openai/typing.py
@@ -107,7 +107,7 @@ class ChatCompletionRequestParams(BaseModel):
     context: str | None = Field(default=None, description="Overwrites the value set by character field.")
     greeting: str | None = Field(default=None, description="Overwrites the value set by character field.")
     user_name: str | None = Field(default=None, description="Your name (the user). By default, it's \"You\".", alias="name1")
-    user_bio: str | None = Field(default=None, description="The user description/personality.")
+    user_bio: str | None = Field(default='', description="The user description/personality.")
     chat_template_str: str | None = Field(default=None, description="Jinja2 template for chat.")
 
     chat_instruct_command: str | None = None