diff --git a/authens/tests/test_backend.py b/authens/tests/test_backend.py
index 3c1556f..d321e88 100644
--- a/authens/tests/test_backend.py
+++ b/authens/tests/test_backend.py
@@ -123,3 +123,12 @@ class TestOldCASBackend(TestCase):
             None, cas_login="johndoe", entrance_year=2014, password="password"
         )
         self.assertEqual(auth_user, user)
+
+    def test_not_migrated_auth(self):
+        user = UserModel.objects.create_user(username="vieilleux", password="password")
+        CASAccount.objects.create(user=user, cas_login="vieilleux", entrance_year=2015)
+
+        auth_user = authenticate(
+            None, cas_login="vieilleux", entrance_year=2015, password="password"
+        )
+        self.assertEqual(auth_user, user)