diff --git a/addons/delivery/stock.py b/addons/delivery/stock.py
index 38f8d0769fc..3c058bf0cf2 100644
--- a/addons/delivery/stock.py
+++ b/addons/delivery/stock.py
@@ -91,9 +91,10 @@ class stock_picking(osv.osv):
                     _('The carrier %s (id: %d) has no delivery grid!') \
                             % (picking.carrier_id.name,
                                 picking.carrier_id.id))
+        quantity = sum([line.product_uom_qty for line in picking.move_lines])
         price = grid_obj.get_price_from_picking(cr, uid, grid_id,
                 invoice.amount_untaxed, picking.weight, picking.volume,
-                context=context)
+                quantity, context=context)
         account_id = picking.carrier_id.product_id.property_account_income.id
         if not account_id:
             account_id = picking.carrier_id.product_id.categ_id\