Session unset_userdata unsetting all user_data

[eluser]RS71[/eluser]
I've been trying to delete certain items from the session but regardless of what I pass unset_userdata(), it deletes all user_data in the DB.

I've tried:

Code:

$data = array(
    'user_id' => '',
    'user_token' => ''
);

$this->CI->session->unset_userdata($data);

and

Code:

$this->CI->session->unset_userdata('user_id');
$this->CI->session->unset_userdata('user_token');

Did I do something wrong?