I must add a new state in my workflow project in

class account_analytic_account(osv.osv):

_name = 'account.analytic.account'

else i get an error like this The value "invoice" for the field "account_analytic_account.state" is not in the selection

Original state 'state': fields.selection([('template', 'Template'),('draft','New'),('open','Open'),('pending','Pending'),('cancelled', 'Cancelled'),('close','Closed')], 'State', required=True,

New state 'state': fields.selection([('template', 'Template'),('invoice','Da Fatturare'),('draft','New'),('open','Open'),('pending','Pending'),('cancelled', 'Cancelled'),('close','Closed')], 'State', required=True,

Is it possible add my custom state in the right position in 'state'?