diff --git a/addons/sale/sale.py b/addons/sale/sale.py
index bee7e90979b..67f04c45fc3 100644
--- a/addons/sale/sale.py
+++ b/addons/sale/sale.py
@@ -732,7 +732,7 @@ class sale_order(osv.osv):
 
         :return: True
         """
-        context = context or {}
+        context = dict(context or {})
         context['lang'] = self.pool['res.users'].browse(cr, uid, uid).lang
         procurement_obj = self.pool.get('procurement.order')
         sale_line_obj = self.pool.get('sale.order.line')