diff -r f951d8e59233 trytond/trytond/modules/sale_shipment_cost/sale.py
--- a/trytond/trytond/modules/sale_shipment_cost/sale.py	Mon May 02 17:16:59 2016 +0200
+++ b/trytond/trytond/modules/sale_shipment_cost/sale.py	Fri Sep 16 12:21:55 2016 +0200
@@ -127,22 +127,16 @@
         cost_line.unit_price = cost_line.amount = cost
         return cost_line
 
-    def create_shipment(self, shipment_type):
-        Shipment = Pool().get('stock.shipment.out')
-
-        shipments = super(Sale, self).create_shipment(shipment_type)
-        if shipment_type == 'out' and shipments and self.carrier:
-            for shipment in shipments:
-                shipment.carrier = self.carrier
-                with Transaction().set_context(
-                        shipment.get_carrier_context()):
-                    cost, currency_id = self.carrier.get_sale_price()
-                Shipment.write([shipment], {
-                        'carrier': self.carrier.id,
-                        'cost': cost,
-                        'cost_currency': currency_id,
-                        })
-        return shipments
+    def _get_shipment_sale(self, Shipment, key):
+        shipment = super(Sale, self)._get_shipment_sale(Shipment, key)
+        if shipment.__name__ == 'stock.shipment.out' and self.carrier:
+            shipment.carrier = self.carrier
+            with Transaction().set_context(
+                    shipment.get_carrier_context()):
+                cost, currency_id = self.carrier.get_sale_price()
+            shipment.cost = cost
+            shipment.cost_currency = currency_id
+        return shipment
 
     def create_invoice(self):
         pool = Pool()