diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index 363fdc620bd..a3ae7197f12 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -194,6 +194,13 @@ class purchase_order(osv.osv):
         ('done', 'Done'),
         ('cancel', 'Cancelled')
     ]
+
+    READONLY_STATES = {
+        'confirmed': [('readonly', True)],
+        'approved': [('readonly', True)],
+        'done': [('readonly', True)]
+    }
+
     _track = {
         'state': {
             'purchase.mt_rfq_confirmed': lambda self, cr, uid, obj, ctx=None: obj.state == 'confirmed',
@@ -222,16 +229,16 @@ class purchase_order(osv.osv):
                                  copy=False),
         'date_approve':fields.date('Date Approved', readonly=1, select=True, copy=False,
                                    help="Date on which purchase order has been approved"),
-        'partner_id':fields.many2one('res.partner', 'Supplier', required=True, states={'confirmed':[('readonly',True)], 'approved':[('readonly',True)],'done':[('readonly',True)]},
+        'partner_id':fields.many2one('res.partner', 'Supplier', required=True, states=READONLY_STATES,
             change_default=True, track_visibility='always'),
         'dest_address_id':fields.many2one('res.partner', 'Customer Address (Direct Delivery)',
-            states={'confirmed':[('readonly',True)], 'approved':[('readonly',True)],'done':[('readonly',True)]},
+            states=READONLY_STATES,
             help="Put an address if you want to deliver directly from the supplier to the customer. " \
                 "Otherwise, keep empty to deliver to your own company."
         ),
-        'location_id': fields.many2one('stock.location', 'Destination', required=True, domain=[('usage','<>','view')], states={'confirmed':[('readonly',True)], 'approved':[('readonly',True)],'done':[('readonly',True)]} ),
-        'pricelist_id':fields.many2one('product.pricelist', 'Pricelist', required=True, states={'confirmed':[('readonly',True)], 'approved':[('readonly',True)],'done':[('readonly',True)]}, help="The pricelist sets the currency used for this purchase order. It also computes the supplier price for the selected products/quantities."),
-        'currency_id': fields.many2one('res.currency','Currency', readonly=True, required=True,states={'draft': [('readonly', False)],'sent': [('readonly', False)]}),
+        'location_id': fields.many2one('stock.location', 'Destination', required=True, domain=[('usage','<>','view')], states=READONLY_STATES),
+        'pricelist_id':fields.many2one('product.pricelist', 'Pricelist', required=True, states=READONLY_STATES, help="The pricelist sets the currency used for this purchase order. It also computes the supplier price for the selected products/quantities."),
+        'currency_id': fields.many2one('res.currency','Currency', required=True, states=READONLY_STATES),
         'state': fields.selection(STATE_SELECTION, 'Status', readonly=True,
                                   help="The status of the purchase order or the quotation request. "
                                        "A request for quotation is a purchase order in a 'Draft' status. "