diff --git a/modoboa/admin/models/alias.py b/modoboa/admin/models/alias.py
index c277f97a8..17aaa01ec 100644
--- a/modoboa/admin/models/alias.py
+++ b/modoboa/admin/models/alias.py
@@ -56,7 +56,7 @@ class Alias(AdminObject):
         return smart_text(self.address)
 
     @classmethod
-    def generate_random_address(self):
+    def generate_random_address(cls):
         """Generate a random address (local part)."""
         m = hashlib.md5()
         for x in random.sample(xrange(10000000), 60):
diff --git a/modoboa/admin/tests/test_alias.py b/modoboa/admin/tests/test_alias.py
index 926b2eabf..eb501114b 100644
--- a/modoboa/admin/tests/test_alias.py
+++ b/modoboa/admin/tests/test_alias.py
@@ -228,6 +228,10 @@ class AliasTestCase(ModoTestCase):
         self.ajax_post(reverse("admin:alias_add"), values)
         self.assertEqual(Alias.objects.count(), alias_count + 1)
 
+        del values["domain"]
+        content = self.ajax_post(reverse("admin:alias_add"), values, 400)
+        self.assertIn("domain", content["form_errors"])
+
     def test_distribution_list_deletion_on_user_update_bug(self):
         """This test demonstrates an issue with distribution list being
            deleted when one of the users which belong to that list is