diff --git a/tests/test_manager.py b/tests/test_manager.py
index 421105ac..3f08bb0c 100644
--- a/tests/test_manager.py
+++ b/tests/test_manager.py
@@ -38,7 +38,7 @@ def manager_user():
     group, created = Group.objects.get_or_create(name='Managers')
     if created:
         group.save()
-    user.groups = [group]
+    user.groups.set([group])
     return user
 
 @pytest.fixture