Session not being destroyed upon the browser closure

[eluser]Refringe[/eluser]
@WanWizard: Could you please elaborate on how to create your "MY_Session" library?

I've created the file:
application/libraries/MY_Session.php

MY_Session.php contents:

Code:

class MY_Session extends CI_Session {
    function MY_Session()
    {
        parent::CI_Session();
        $this->sess_expiration = 0;
    }
}

Then to load MY_Session I add it to the autoload array in:
application/config/config.php

Code:

$autoload['libraries'] = array('session', 'my_session');

Is this correct?