diff --git a/addons/mail/models/mail_message.py b/addons/mail/models/mail_message.py
index 4ef8133eaef..e584d1ee3b3 100644
--- a/addons/mail/models/mail_message.py
+++ b/addons/mail/models/mail_message.py
@@ -663,6 +663,8 @@ class Message(models.Model):
     def unlink(self):
         # cascade-delete attachments that are directly attached to the message (should only happen
         # for mail.messages that act as parent for a standalone mail.mail record).
+        # the cache of the related document doesn't need to be invalidate (see @_invalidate_documents)
+        # because the unlink method invalidates the whole cache anyway
         if not self:
             return True
         self.check_access_rule('unlink')
@@ -674,8 +676,6 @@ class Message(models.Model):
         for elem in self:
             for partner in elem.partner_ids & partners_with_user:
                 messages_by_partner[partner] |= elem
-            if elem.is_thread_message():
-                elem._invalidate_documents()
 
         # Notify front-end of messages deletion for partners having a user
         if messages_by_partner:
diff --git a/addons/test_mass_mailing/tests/test_performance.py b/addons/test_mass_mailing/tests/test_performance.py
index cb1e5c9b8ae..70dec0d4677 100644
--- a/addons/test_mass_mailing/tests/test_performance.py
+++ b/addons/test_mass_mailing/tests/test_performance.py
@@ -54,7 +54,7 @@ class TestMassMailPerformance(TestMassMailPerformanceBase):
         self.assertEqual(mailing.delivered, 50)
 
         # runbot needs +3 compared to local
-        with self.assertQueryCount(__system__=68, marketing=67):  # tm 66/66
+        with self.assertQueryCount(__system__=18, marketing=17):  # tm 15/15
             self.env['mail.mail'].sudo().search([('to_delete', '=', True)]).unlink()
 
         mails = self.env['mail.mail'].sudo().search([('mailing_id', '=', mailing.id)])
@@ -101,7 +101,7 @@ class TestMassMailBlPerformance(TestMassMailPerformanceBase):
         self.assertEqual(mailing.delivered, 50)
 
         # runbot needs +3 compared to local
-        with self.assertQueryCount(__system__=68, marketing=67):  # tm 66/66
+        with self.assertQueryCount(__system__=18, marketing=17):  # tm 15/15
             self.env['mail.mail'].sudo().search([('to_delete', '=', True)]).unlink()
 
         cancelled_mail_count = self.env['mail.mail'].sudo().search([('mailing_id', '=', mailing.id)])