diff --git a/models/sale_order.py b/models/sale_order.py
index 12876e46c4c..d4b8f895989 100644
--- a/models/sale_order.py
+++ b/models/sale_order.py
@@ -37,9 +37,8 @@ class SaleOrder(models.Model):
             order._update_existing_reward_lines()
 
     def copy(self, default=None):
-        order = super(SaleOrder, self).copy(dict(default or {}, order_line=False))
-        for line in self._get_reward_lines():
-            line.copy({'order_id': order.id})
+        order = super(SaleOrder, self).copy(default)
+        order._get_reward_lines().unlink()
         order.with_context(sale_coupon_no_loop=False)._create_new_no_code_promo_reward_lines()
         return order