php - Datamapper and CI: is not a valid parent relationship -

i have 2 models tables need relate, campus:

class campus extends datamapper {      var $table='campi';     var $has_many=array('boleto');          function __construct()  {         parent::__construct();       } } 

and boleto:

class boleto extends datamapper {      var $table='boletos';     var $has_one=array('campus');        function __construct(){         parent::__construct();     }  } 

i have been working these tables 5 months, have relation table:

| id | boleto_id | campus_id | 

everything ok, recently, every time need make includes relation got error message:

datamapper error: 'boleto' not valid parent relationship campus. relationships configured correctly?

do know what's happening? can't find error. strange that, said, working.

thanks in advance!

table boletos:

| id | folio | 

table campi:

| id | nombre_campus | 

table boletos_campi:

| id | boleto_id | campus_id | 

i'm trying code (as working before have relation saved):

$b = new boleto(); $b->where('id',20114)->get(); $b->campus->get();