diff --git a/addons/website_forum/models/forum.py b/addons/website_forum/models/forum.py
index 59b22290fee..ebe6bd80b2d 100644
--- a/addons/website_forum/models/forum.py
+++ b/addons/website_forum/models/forum.py
@@ -427,6 +427,11 @@ class Post(models.Model):
                 raise KarmaError('User karma not sufficient to post an image or link.')
         return content
 
+    @api.constrains('parent_id')
+    def _check_parent_id(self):
+        if not self._check_recursion():
+            raise ValidationError(_('You cannot create recursive forum posts.'))
+
     @api.model
     def create(self, vals):
         if 'content' in vals and vals.get('forum_id'):