protected function setDefaults(array $defaultOptions = array())
    {
        $defaultOptions = array_merge(array(
            'depth' => null,
            'ancestorCurrencyDepth' => null,
            'currentClass' => 'active',
            'ancestorClass' => 'active',
            'firstClass' => null,
            'lastClass' => null
        ), $defaultOptions);

        parent::setDefaults($defaultOptions);
    }