diff --git a/modoboa/admin/api/v2/tests.py b/modoboa/admin/api/v2/tests.py
index db5881cbb..472c87e33 100644
--- a/modoboa/admin/api/v2/tests.py
+++ b/modoboa/admin/api/v2/tests.py
@@ -536,9 +536,10 @@ class AliasViewSetTestCase(ModoAPITestCase):
         data = {"address": "alias@test.com"}
         resp = self.client.post(url, data, format="json")
         self.assertEqual(resp.status_code, 400)
-
-        al_id = models.Alias.objects.get(address="alias@test.com").pk
-        self.assertEqual(resp.json()["id"], al_id)
+        self.assertEqual(
+            resp.json()["address"][0],
+            "This alias already exists"
+        )
 
         data = {"address": "alias2@test.com"}
         resp = self.client.post(url, data, format="json")