diff -r dba965a72938 sale.py
--- a/trytond/trytond/modules/sale/sale.py	Tue Oct 06 10:07:07 2015 +0200
+++ b/trytond/trytond/modules/sale/sale.py	Tue Oct 06 10:09:08 2015 +0200
@@ -1132,7 +1132,6 @@
         return 2

     def get_move_done(self, name):
-        Uom = Pool().get('product.uom')
         done = True
         if not self.product:
             return True
@@ -1146,7 +1145,7 @@
                     and move.id not in skip_ids:
                 done = False
                 break
-            quantity -= Uom.compute_qty(move.uom, move.quantity, self.unit)
+            quantity -= move.origin_quantity
         if done:
             if quantity > 0.0:
                 done = False
@@ -1356,8 +1355,7 @@
             quantity = 0.0
             for move in self.moves:
                 if move.state == 'done':
-                    quantity += Uom.compute_qty(move.uom, move.quantity,
-                        self.unit)
+                    quantity += move.origin_quantity
                     if move.invoiced_quantity < move.quantity:
                         stock_moves.append(move)
         if self.sale.shipment_method == 'order':
@@ -1371,8 +1369,7 @@
             if old_invoice_line.id not in skip_ids:
                 sign = (1.0 if invoice_type == old_invoice_line.invoice_type
                     else -1.0)
-                quantity -= Uom.compute_qty(old_invoice_line.unit,
-                    sign * old_invoice_line.quantity, self.unit)
+                quantity -= sign * old_invoice_line.origin_quantity

         rounding = self.unit.rounding if self.unit else 0.01
         invoice_line.quantity = Uom.round(quantity, rounding)