diff --git a/addons/mail/models/mail_thread.py b/addons/mail/models/mail_thread.py
index bd538fe7a39..f7cddd2525d 100644
--- a/addons/mail/models/mail_thread.py
+++ b/addons/mail/models/mail_thread.py
@@ -1926,7 +1926,7 @@ class MailThread(models.AbstractModel):
     def message_post(self, body='', subject=None,
                      message_type='notification', subtype=None,
                      parent_id=False, attachments=None,
-                     notif_layout=False, add_sign=False, model_description=False,
+                     notif_layout=False, add_sign=True, model_description=False,
                      mail_auto_delete=True, **kwargs):
         """ Post a new message in an existing thread, returning the new
             mail.message ID.