diff --git a/addons/stock/stock.py b/addons/stock/stock.py
index 3b6bb70e457..16565871de3 100644
--- a/addons/stock/stock.py
+++ b/addons/stock/stock.py
@@ -721,8 +721,8 @@ class stock_picking(osv.osv):
         if ('name' not in default) or (picking_obj.name == '/'):
             seq_obj_name = 'stock.picking.' + picking_obj.type
             default['name'] = self.pool.get('ir.sequence').get(cr, uid, seq_obj_name)
-            default['origin'] = ''
-            default['backorder_id'] = False
+            default.setdefault('origin', False)
+            default.setdefault('backorder_id', False)
         if 'invoice_state' not in default and picking_obj.invoice_state == 'invoiced':
             default['invoice_state'] = '2binvoiced'
         res = super(stock_picking, self).copy(cr, uid, id, default, context)