diff --git a/aiogram/utils/chat_member.py b/aiogram/utils/chat_member.py
index 9d86823d..7ac666c5 100644
--- a/aiogram/utils/chat_member.py
+++ b/aiogram/utils/chat_member.py
@@ -24,7 +24,7 @@ ChatMemberUnion = Union[
 
 ChatMemberCollection = Tuple[Type[ChatMember], ...]
 
-ChatMemberAdapter = TypeAdapter(
+ChatMemberAdapter: TypeAdapter[ChatMemberUnion] = TypeAdapter(
     Annotated[
         ChatMemberUnion,
         Field(discriminator="status"),