diff --git a/addons/mail/models/ir_attachment.py b/addons/mail/models/ir_attachment.py
index 527b22409d6..ee51ed8382e 100644
--- a/addons/mail/models/ir_attachment.py
+++ b/addons/mail/models/ir_attachment.py
@@ -15,19 +15,6 @@ class IrAttachment(models.Model):
         for record in self:
             record.register_as_main_attachment(force=False)
 
-    @api.multi
-    def unlink(self):
-        self.remove_as_main_attachment()
-        super(IrAttachment, self).unlink()
-
-    @api.multi
-    def remove_as_main_attachment(self):
-        for attachment in self:
-            related_record = self.env[attachment.res_model].browse(attachment.res_id)
-            if related_record and hasattr(related_record, 'message_main_attachment_id'):
-                if related_record.message_main_attachment_id == attachment:
-                    related_record.message_main_attachment_id = False
-
     def register_as_main_attachment(self, force=True):
         """ Registers this attachment as the main one of the model it is
         attached to.