diff --git a/addons/mail/tests/test_mail.py b/addons/mail/tests/test_mail.py
index 02b55cef9f7..a48935ceed6 100644
--- a/addons/mail/tests/test_mail.py
+++ b/addons/mail/tests/test_mail.py
@@ -506,10 +506,11 @@ class test_mail(test_mail_mockup.TestMailMockups):
         self.assertEqual(compose.parent_id and compose.parent_id.id, message.id, 'mail.message parent_id incorrect')
         # Test: mail.message: attachments
         for attach in compose.attachment_ids:
-            self.assertEqual(attach.res_model, 'mail.group', 'mail.message attachment res_model incorrect')
-            self.assertEqual(attach.res_id, self.group_pigs_id, 'mail.message attachment res_id incorrect')
+            # this test is commented: the field one2many became many2many
+            # self.assertEqual(attach.res_model, 'mail.group', 'mail.message attachment res_model incorrect')
+            # self.assertEqual(attach.res_id, self.group_pigs_id, 'mail.message attachment res_id incorrect')
             self.assertIn((attach.datas_fname, attach.datas.decode('base64')), _attachments_test, 'mail.message attachment name / data incorrect')
-
+       
         # ----------------------------------------
         # CASE3: mass_mail on Pigs and Bird
         # ----------------------------------------