diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index fcabd0b8cec..ec611536c80 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -422,6 +422,7 @@ class purchase_order(osv.osv):
         if not inv_ids:
             raise UserError(_('Please create Invoices.'))
         result['domain'] = [('id', 'in', inv_ids)]
+        return result
 
     def view_invoice(self, cr, uid, ids, context=None):
         '''