diff --git a/aleksis/apps/chronos/migrations/0001_initial.py b/aleksis/apps/chronos/migrations/0001_initial.py
index 1b1c0ee95b474e02006d6d7c983bc3619176fca7..883b25bbf97f4bb0660e787d0a787b754b5efec4 100644
--- a/aleksis/apps/chronos/migrations/0001_initial.py
+++ b/aleksis/apps/chronos/migrations/0001_initial.py
@@ -305,7 +305,7 @@ class Migration(migrations.Migration):
                 "verbose_name_plural": "Supervision substitutions",
                 "ordering": ["date", "supervision"],
             },
-            managers=[("objects", django.contrib.sites.managers.CurrentSiteManager()),],
+            managers=[],
         ),
         migrations.CreateModel(
             name="SupervisionArea",
diff --git a/aleksis/apps/chronos/migrations/0007_unique_constraints.py b/aleksis/apps/chronos/migrations/0007_unique_constraints.py
new file mode 100644
index 0000000000000000000000000000000000000000..754c3ae1c1c9c7a8a4e3ab6f616a459cf65d5298
--- /dev/null
+++ b/aleksis/apps/chronos/migrations/0007_unique_constraints.py
@@ -0,0 +1,85 @@
+# Generated by Django 3.2.3 on 2021-05-22 12:06
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('chronos', '0006_indexes'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='chronosglobalpermissions',
+            options={'managed': False, 'permissions': (('view_all_room_timetables', 'Can view all room timetables'), ('view_all_group_timetables', 'Can view all group timetables'), ('view_all_person_timetables', 'Can view all person timetables'), ('view_timetable_overview', 'Can view timetable overview'), ('view_lessons_day', 'Can view all lessons per day'))},
+        ),
+        migrations.AlterField(
+            model_name='room',
+            name='short_name',
+            field=models.CharField(max_length=255, verbose_name='Short name'),
+        ),
+        migrations.AlterField(
+            model_name='subject',
+            name='name',
+            field=models.CharField(max_length=255, verbose_name='Long name'),
+        ),
+        migrations.AlterField(
+            model_name='subject',
+            name='short_name',
+            field=models.CharField(max_length=255, verbose_name='Short name'),
+        ),
+        migrations.AlterField(
+            model_name='timeperiod',
+            name='weekday',
+            field=models.PositiveSmallIntegerField(choices=[(0, 'Montag'), (1, 'Dienstag'), (2, 'Mittwoch'), (3, 'Donnerstag'), (4, 'Freitag'), (5, 'Samstag'), (6, 'Sonntag')], verbose_name='Week day'),
+        ),
+        migrations.AlterUniqueTogether(
+            name='lessonsubstitution',
+            unique_together=set(),
+        ),
+        migrations.AlterUniqueTogether(
+            name='timeperiod',
+            unique_together=set(),
+        ),
+        migrations.AlterUniqueTogether(
+            name='validityrange',
+            unique_together=set(),
+        ),
+        migrations.AddConstraint(
+            model_name='absencereason',
+            constraint=models.UniqueConstraint(fields=('site_id', 'short_name'), name='unique_short_name_per_site_absence_reason'),
+        ),
+        migrations.AddConstraint(
+            model_name='break',
+            constraint=models.UniqueConstraint(fields=('site_id', 'short_name'), name='unique_short_name_per_site_break'),
+        ),
+        migrations.AddConstraint(
+            model_name='lessonsubstitution',
+            constraint=models.UniqueConstraint(fields=('lesson_period', 'week'), name='unique_period_per_week'),
+        ),
+        migrations.AddConstraint(
+            model_name='room',
+            constraint=models.UniqueConstraint(fields=('site_id', 'short_name'), name='unique_short_name_per_site_room'),
+        ),
+        migrations.AddConstraint(
+            model_name='subject',
+            constraint=models.UniqueConstraint(fields=('site_id', 'short_name'), name='unique_short_name_per_site_subject'),
+        ),
+        migrations.AddConstraint(
+            model_name='subject',
+            constraint=models.UniqueConstraint(fields=('site_id', 'name'), name='unique_name_per_site'),
+        ),
+        migrations.AddConstraint(
+            model_name='supervisionarea',
+            constraint=models.UniqueConstraint(fields=('site_id', 'short_name'), name='unique_short_name_per_site_supervision_area'),
+        ),
+        migrations.AddConstraint(
+            model_name='timeperiod',
+            constraint=models.UniqueConstraint(fields=('weekday', 'period', 'validity'), name='unique_period_per_range'),
+        ),
+        migrations.AddConstraint(
+            model_name='validityrange',
+            constraint=models.UniqueConstraint(fields=('school_term', 'date_start', 'date_end'), name='unique_dates_per_term'),
+        ),
+    ]