diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index a5e1f24b6e3..1fc2e1c74f8 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -725,6 +725,7 @@ class purchase_order(osv.osv):
             'invoiced':False,
             'invoice_ids': [],
             'picking_ids': [],
+            'partner_ref': '',
             'name': self.pool.get('ir.sequence').get(cr, uid, 'purchase.order'),
         })
         return super(purchase_order, self).copy(cr, uid, id, default, context)
diff --git a/addons/sale/sale.py b/addons/sale/sale.py
index 616d625d8bf..668685ed342 100644
--- a/addons/sale/sale.py
+++ b/addons/sale/sale.py
@@ -74,6 +74,7 @@ class sale_order(osv.osv):
             'state': 'draft',
             'invoice_ids': [],
             'date_confirm': False,
+            'client_order_ref': '',
             'name': self.pool.get('ir.sequence').get(cr, uid, 'sale.order'),
         })
         return super(sale_order, self).copy(cr, uid, id, default, context=context)