diff --git a/addons/project/models/project.py b/addons/project/models/project.py
index 4064e001f8f..ed029b1a4f3 100644
--- a/addons/project/models/project.py
+++ b/addons/project/models/project.py
@@ -270,7 +270,7 @@ class Project(models.Model):
     def message_subscribe(self, partner_ids=None, channel_ids=None, subtype_ids=None, force=True):
         """ Subscribe to all existing active tasks when subscribing to a project """
         res = super(Project, self).message_subscribe(partner_ids=partner_ids, channel_ids=channel_ids, subtype_ids=subtype_ids, force=force)
-        if not subtype_ids or any(subtype.parent_id.model == 'project.task' for subtype in self.env['mail.message.subtype'].browse(subtype_ids)):
+        if not subtype_ids or any(subtype.parent_id.res_model == 'project.task' for subtype in self.env['mail.message.subtype'].browse(subtype_ids)):
             for partner_id in partner_ids or []:
                 self.mapped('tasks').filtered(lambda task: not task.stage_id.fold and partner_id not in task.message_partner_ids.ids).message_subscribe(
                     partner_ids=[partner_id], channel_ids=None, subtype_ids=None, force=False)