diff --git a/addons/event_sale/models/sale_order.py b/addons/event_sale/models/sale_order.py
index 01de46bdc4334c8f2da041b3bf5fd916e1fa2cda..81e35d999113d56949c1fedc4922ae770cde005e 100644
--- a/addons/event_sale/models/sale_order.py
+++ b/addons/event_sale/models/sale_order.py
@@ -25,7 +25,7 @@ class SaleOrder(models.Model):
         return res
 
     def unlink(self):
-        self.order_line._unlink_associated_registrations()
+        self.mapped('order_line')._unlink_associated_registrations()
         super(SaleOrder, self).unlink()