diff --git a/addons/stock_account/stock.py b/addons/stock_account/stock.py
index b965f6689d7..486c94d797f 100644
--- a/addons/stock_account/stock.py
+++ b/addons/stock_account/stock.py
@@ -293,8 +293,8 @@ class stock_picking(osv.osv):
             else:
                 invoice = invoice_obj.browse(cr, uid, invoices[key], context=context)
                 if not invoice.origin or invoice_vals['origin'] not in invoice.origin.split(', '):
-                    origin = filter(None, [invoice.origin, invoice_vals['origin']])
-                    invoice.write({'origin': ', '.join(origin)})
+                    invoice_origin = filter(None, [invoice.origin, invoice_vals['origin']])
+                    invoice.write({'origin': ', '.join(invoice_origin)})
 
             invoice_line_vals = move_obj._get_invoice_line_vals(cr, uid, move, partner, inv_type, context=context)
             invoice_line_vals['invoice_id'] = invoices[key]