diff --git a/addons/sale_product_matrix/models/sale_order.py b/addons/sale_product_matrix/models/sale_order.py
index 783b31647c0..a7dfee8457c 100644
--- a/addons/sale_product_matrix/models/sale_order.py
+++ b/addons/sale_product_matrix/models/sale_order.py
@@ -106,6 +106,8 @@ class SaleOrder(models.Model):
                 self.update(dict(order_line=new_lines))
                 for line in self.order_line.filtered(lambda line: line.product_template_id == product_template):
                     line.product_id_change()
+                    line._onchange_discount()
+                    
 
     def _get_matrix(self, product_template):
         """Return the matrix of the given product, updated with current SOLines quantities.