diff --git a/addons/mail/models/mail_message.py b/addons/mail/models/mail_message.py
index e46d2663a45..1ca454b6897 100644
--- a/addons/mail/models/mail_message.py
+++ b/addons/mail/models/mail_message.py
@@ -135,7 +135,7 @@ class Message(models.Model):
     # mainly usefull for testing
     notified_partner_ids = fields.Many2many(
         'res.partner', 'mail_notification', string='Partners with Need Action',
-        context={'active_test': False}, depends=['notification_ids'])
+        context={'active_test': False}, depends=['notification_ids'], copy=False)
     needaction = fields.Boolean(
         'Need Action', compute='_compute_needaction', search='_search_needaction')
     has_error = fields.Boolean(
diff --git a/addons/test_mail/tests/test_message_post.py b/addons/test_mail/tests/test_message_post.py
index c43089c7f85..49472beec66 100644
--- a/addons/test_mail/tests/test_message_post.py
+++ b/addons/test_mail/tests/test_message_post.py
@@ -294,6 +294,10 @@ class TestMessageNotify(TestMessagePostCommon):
         )
         self.assertNotIn(new_notification, self.test_record.message_ids)
 
+        # notified_partner_ids should be empty after copying the message
+        copy = new_notification.copy()
+        self.assertFalse(copy.notified_partner_ids)
+
         admin_mails = [mail for mail in self._mails if self.partner_admin.name in mail.get('email_to')[0]]
         self.assertEqual(len(admin_mails), 1, 'There should be exactly one email sent to admin')
         admin_mail_body = admin_mails[0].get('body')