session in 3.0.3 not saving userdata

I've test, but it okay ??

$this->load->library('session');
$this->session->set_userdata(array('email'=>'[email protected]', 'is_login'=>1));
$session = $this->session->userdata();
var_dump($session);

array(3) { ["__ci_last_regenerate"]=> int(1448684634) ["email"]=> string(17) "[email protected]" ["is_login"]=> int(1) }