diff --git a/aleksis/apps/chronos/util/predicates.py b/aleksis/apps/chronos/util/predicates.py
index bc9c8d92f419b605302a782a9617025a1437f1cc..e7b3a31d022bd8c7f542b983dad6a69c29888f73 100644
--- a/aleksis/apps/chronos/util/predicates.py
+++ b/aleksis/apps/chronos/util/predicates.py
@@ -13,9 +13,9 @@ def has_timetable_perm(user: User, obj: Model) -> bool:
     """Predicate which checks whether the user is allowed to access the requested timetable."""
     if type(obj) is Group:
         return (
-            user.person.member_of.filter(id=obj.id).exists()
+            obj in user.person.member_of.all()
             or user.person.primary_group == obj
-            or user.person.owner_of.filter(id=obj.id).exists()
+            or obj in user.person.owner_of.all()
             or has_global_perm("chronos.view_all_group_timetables")(user)
             or has_object_perm("core.view_group_timetable")(user, obj)
         )