diff --git a/tests/test__auth.py b/tests/test__auth.py
index 9c4ea65c8dd..6347e42d659 100644
--- a/tests/test__auth.py
+++ b/tests/test__auth.py
@@ -89,7 +89,7 @@ class CredentialsWithScopes(
 
         self.assertNotEqual(credentials, returned)
         self.assertEqual(returned, credentials.with_scopes.return_value)
-        credentials.with_scopes.assert_called_once_with(mock.sentinel.scopes)
+        credentials.with_scopes.assert_called_once_with(mock.sentinel.scopes, default_scopes=None)
 
     def test_authorized_http(self):
         credentials = mock.Mock(spec=google.auth.credentials.Credentials)