diff --git a/addons/sale_stock/sale_stock.py b/addons/sale_stock/sale_stock.py
index 48f11ed316e..4cca4aeda79 100644
--- a/addons/sale_stock/sale_stock.py
+++ b/addons/sale_stock/sale_stock.py
@@ -445,11 +445,12 @@ class stock_picking(osv.osv):
         """ Inherit the original function of the 'stock' module
             We select the partner of the sales order as the partner of the customer invoice
         """
-        saleorder_ids = self.pool['sale.order'].search(cr, uid, [('procurement_group_id' ,'=', picking.group_id.id)], context=context)
-        saleorders = self.pool['sale.order'].browse(cr, uid, saleorder_ids, context=context)
-        if saleorders and saleorders[0] and saleorders[0].order_policy == 'picking':
-            saleorder = saleorders[0]
-            return saleorder.partner_invoice_id.id
+        if picking.sale_id:
+            saleorder_ids = self.pool['sale.order'].search(cr, uid, [('procurement_group_id' ,'=', picking.group_id.id)], context=context)
+            saleorders = self.pool['sale.order'].browse(cr, uid, saleorder_ids, context=context)
+            if saleorders and saleorders[0] and saleorders[0].order_policy == 'picking':
+                saleorder = saleorders[0]
+                return saleorder.partner_invoice_id.id
         return super(stock_picking, self)._get_partner_to_invoice(cr, uid, picking, context=context)
     
     def _get_sale_id(self, cr, uid, ids, name, args, context=None):