diff --git a/addons/purchase/wizard/wizard_group.py b/addons/purchase/wizard/wizard_group.py
index 8c0bc2dd319..0ddfec5fbce 100644
--- a/addons/purchase/wizard/wizard_group.py
+++ b/addons/purchase/wizard/wizard_group.py
@@ -1,7 +1,7 @@
 # -*- encoding: utf-8 -*-
 ##############################################################################
 #
-#    OpenERP, Open Source Management Solution	
+#    OpenERP, Open Source Management Solution
 #    Copyright (C) 2004-2009 Tiny SPRL (<http://tiny.be>). All Rights Reserved
 #    $Id$
 #
@@ -25,7 +25,7 @@ import time
 import wizard
 import netsvc
 import pooler
-from osv.orm import browse_record
+from osv.orm import browse_record, browse_null
 
 merge_form = """<?xml version="1.0"?>
 <form string="Merge orders">
@@ -45,18 +45,21 @@ ack_form = """<?xml version="1.0"?>
 
 ack_fields = {}
 
-def _mergeOrders(self, cr, uid, data, context):
+
+def _merge_orders(self, cr, uid, data, context):
     order_obj = pooler.get_pool(cr.dbname).get('purchase.order')
 
     def make_key(br, fields):
         list_key = []
         for field in fields:
             field_val = getattr(br, field)
-            if field in ('product_id','move_dest_id', 'account_analytic_id'):
+            if field in ('product_id', 'move_dest_id', 'account_analytic_id'):
                 if not field_val:
                     field_val = False
             if isinstance(field_val, browse_record):
                 field_val = field_val.id
+            elif isinstance(field_val, browse_null):
+                field_val = False
             elif isinstance(field_val, list):
                 field_val = ((6, 0, tuple([v.id for v in field_val])),)
             list_key.append((field, field_val))
@@ -67,6 +70,7 @@ def _mergeOrders(self, cr, uid, data, context):
     new_orders = {}
     for porder in [order for order in order_obj.browse(cr, uid, data['ids']) if order.state == 'draft']:
         order_key = make_key(porder, ('partner_id', 'location_id'))
+
         new_order = new_orders.setdefault(order_key, ({}, []))
         new_order[1].append(porder.id)
         order_infos = new_order[0]
@@ -89,7 +93,7 @@ def _mergeOrders(self, cr, uid, data, context):
             if porder.notes:
                 order_infos['notes'] += ('\n%s' % (porder.notes,))
             if porder.origin:
-                order_infos['origin'] = order_infos['origin'] +' '+ porder.origin
+                order_infos['origin'] = order_infos['origin'] + ' ' + porder.origin
 
         for order_line in porder.order_line:
             line_key = make_key(order_line, ('name', 'date_planned', 'taxes_id', 'price_unit', 'notes', 'product_id', 'move_dest_id', 'account_analytic_id'))
@@ -103,7 +107,7 @@ def _mergeOrders(self, cr, uid, data, context):
                     field_val = getattr(order_line, field)
                     if isinstance(field_val, browse_record):
                         field_val = field_val.id
-                    o_line[field] = field_val 
+                    o_line[field] = field_val
                 o_line['uom_factor'] = order_line.product_uom and order_line.product_uom.factor or 1.0
 
     wf_service = netsvc.LocalService("workflow")
@@ -120,6 +124,7 @@ def _mergeOrders(self, cr, uid, data, context):
             del value['uom_factor']
             value.update(dict(key))
         order_data['order_line'] = [(0, 0, value) for value in order_data['order_line'].itervalues()]
+
         # create the new order
         neworder_id = order_obj.create(cr, uid, order_data)
         allorders.append(neworder_id)
@@ -130,8 +135,8 @@ def _mergeOrders(self, cr, uid, data, context):
             wf_service.trg_validate(uid, 'purchase.order', old_id, 'purchase_cancel', cr)
 
     return {
-        'domain': "[('id','in', ["+','.join(map(str,allorders))+"])]",
-        'name': 'Purchase orders',
+        'domain': "[('id','in', [" + ','.join(map(str, allorders)) + "])]",
+        'name': 'Purchase Orders',
         'view_type': 'form',
         'view_mode': 'tree,form',
         'res_model': 'purchase.order',
@@ -139,18 +144,18 @@ def _mergeOrders(self, cr, uid, data, context):
         'type': 'ir.actions.act_window'
     }
 
+
 class merge_orders(wizard.interface):
     states = {
-        'init' : {
-            'actions' : [],
-            'result' : {'type' : 'form', 'arch' : merge_form, 'fields' : merge_fields, 'state' : [('end', 'Cancel'),('merge', 'Merge orders') ]}
+        'init': {
+            'actions': [],
+            'result': {'type': 'form', 'arch' : merge_form, 'fields' : merge_fields, 'state' : [('end', 'Cancel'), ('merge', 'Merge orders') ]}
         },
-        'merge' : {
-            'actions' : [],
-            'result' : {'type':'action', 'action':_mergeOrders, 'state':'end'}
+        'merge': {
+            'actions': [],
+            'result': {'type': 'action', 'action': _merge_orders, 'state': 'end'}
         },
     }
+
 merge_orders("purchase.order.merge")
 
-# vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4:
-