diff --git a/trytond/res/user.py b/trytond/res/user.py
index a7a3cd9937..df20602b25 100644
--- a/trytond/res/user.py
+++ b/trytond/res/user.py
@@ -546,7 +546,7 @@ class Warning_(ModelSQL, ModelView):
             ])
         if not warnings:
             return True
-        cls.delete([x.id for x in warnings if not x.always])
+        cls.delete([x for x in warnings if not x.always])
         return False