diff --git a/instaloader/instaloadercontext.py b/instaloader/instaloadercontext.py
index 858b65d..c045810 100644
--- a/instaloader/instaloadercontext.py
+++ b/instaloader/instaloadercontext.py
@@ -101,7 +101,7 @@ class InstaloaderContext:
         self.user_agent = user_agent if user_agent is not None else default_user_agent()
         self.request_timeout = request_timeout
         self._session = self.get_anonymous_session()
-        self.username = None
+        self.username: Optional[str] = None
         self.user_id = None
         self.sleep = sleep
         self.quiet = quiet