diff --git a/django/contrib/auth/create_superuser.py b/django/contrib/auth/create_superuser.py
index f42d30539e..2e93c35b93 100644
--- a/django/contrib/auth/create_superuser.py
+++ b/django/contrib/auth/create_superuser.py
@@ -46,6 +46,7 @@ def createsuperuser(username=None, email=None, password=None):
             if not username.isalnum():
                 sys.stderr.write("Error: That username is invalid. Use only letters, digits and underscores.\n")
                 username = None
+                continue
             try:
                 User.objects.get(username=username)
             except User.DoesNotExist: