diff --git a/codalab/lib/codalab_manager.py b/codalab/lib/codalab_manager.py
index f1ddddc28..aa8c4ae2d 100644
--- a/codalab/lib/codalab_manager.py
+++ b/codalab/lib/codalab_manager.py
@@ -491,6 +491,7 @@ def _cache_token(token_info, username=None):
             print('Requesting access at %s' % cache_key)
         if username is None:
             sys.stdout.write('Username: ')  # Use write to avoid extra space
+            sys.stdout.flush()
             username = sys.stdin.readline().rstrip()
         if password is None:
             password = getpass.getpass()