php - CodeIgniter DataMapper Problem with Relationship -

hey i've got pretty simple relationship in datamapper model..

in model ticket hav:

var $has_one = array("user"); 

and when try

$ticket->user->get()->username; 

it says:

datamapper error: 'ticket' not valid parent relationship user. relationships configured correctly?

i dont see problem :/

what user model like? map ticket well?

var $has_many = array("ticket");