diff --git a/sale.py b/sale.py
index 8dd0ab5..6a4dab1 100644
--- a/sale.py
+++ b/sale.py
@@ -42,7 +42,7 @@ class Sale:
     def default_sale_device():
         User = Pool().get('res.user')
         user = User(Transaction().user)
-        return user.sale_device or None
+        return user.sale_device.id or None
 
     @classmethod
     def get_paid_amount(cls, sales, names):