diff --git a/authority/migrations/0001_initial.py b/authority/migrations/0001_initial.py
index f17f6db..35c251d 100644
--- a/authority/migrations/0001_initial.py
+++ b/authority/migrations/0001_initial.py
@@ -24,10 +24,10 @@ class Migration(migrations.Migration):
                 ('approved', models.BooleanField(default=False, help_text='Designates whether the permission has been approved and treated as active. Unselect this instead of deleting permissions.', verbose_name='approved')),
                 ('date_requested', models.DateTimeField(default=datetime.datetime.now, verbose_name='date requested')),
                 ('date_approved', models.DateTimeField(null=True, verbose_name='date approved', blank=True)),
-                ('content_type', models.ForeignKey(related_name='row_permissions', to='contenttypes.ContentType')),
-                ('creator', models.ForeignKey(related_name='created_permissions', blank=True, to=settings.AUTH_USER_MODEL, null=True)),
-                ('group', models.ForeignKey(blank=True, to='auth.Group', null=True)),
-                ('user', models.ForeignKey(related_name='granted_permissions', blank=True, to=settings.AUTH_USER_MODEL, null=True)),
+                ('content_type', models.ForeignKey(related_name='row_permissions', to='contenttypes.ContentType', on_delete=models.CASCADE)),
+                ('creator', models.ForeignKey(related_name='created_permissions', blank=True, to=settings.AUTH_USER_MODEL, null=True, on_delete=models.CASCADE)),
+                ('group', models.ForeignKey(blank=True, to='auth.Group', null=True, on_delete=models.CASCADE)),
+                ('user', models.ForeignKey(related_name='granted_permissions', blank=True, to=settings.AUTH_USER_MODEL, null=True, on_delete=models.CASCADE)),
             ],
             options={
                 'verbose_name': 'permission',
diff --git a/authority/models.py b/authority/models.py
index d6cca3b..174aed7 100644
--- a/authority/models.py
+++ b/authority/models.py
@@ -16,15 +16,15 @@ class Permission(models.Model):
     of any content type.
     """
     codename = models.CharField(_('codename'), max_length=100)
-    content_type = models.ForeignKey(ContentType, related_name="row_permissions")
+    content_type = models.ForeignKey(ContentType, related_name="row_permissions", on_delete=models.CASCADE)
     object_id = models.PositiveIntegerField()
     content_object = GenericForeignKey('content_type', 'object_id')
 
     user = models.ForeignKey(
-        user_model_label, null=True, blank=True, related_name='granted_permissions')
-    group = models.ForeignKey(Group, null=True, blank=True)
+        user_model_label, null=True, blank=True, related_name='granted_permissions', on_delete=models.CASCADE)
+    group = models.ForeignKey(Group, null=True, blank=True, on_delete=models.CASCADE)
     creator = models.ForeignKey(
-        user_model_label, null=True, blank=True, related_name='created_permissions')
+        user_model_label, null=True, blank=True, related_name='created_permissions', on_delete=models.CASCADE)
 
     approved = models.BooleanField(
         _('approved'),