diff --git a/addons/delivery/models/sale_order.py b/addons/delivery/models/sale_order.py
index b635ec7d801..753223647e9 100644
--- a/addons/delivery/models/sale_order.py
+++ b/addons/delivery/models/sale_order.py
@@ -31,7 +31,14 @@ class SaleOrder(models.Model):
     @api.depends('carrier_id', 'partner_id', 'order_line')
     def _compute_delivery_price(self):
         for order in self:
-            order.delivery_price = order.carrier_id.with_context(order_id=order.id).price
+            if order.state != 'draft':
+                # we do not want to recompute the shipping price of an already validated/done SO
+                continue
+            elif order.carrier_id.delivery_type != 'grid' and not order.order_line:
+                # prevent SOAP call to external shipping provider when SO has no lines yet
+                continue
+            else:
+                order.delivery_price = order.carrier_id.with_context(order_id=order.id).price
 
     @api.multi
     def delivery_set(self):