public function setConfig($config)
    {
        if (is_null($config)) {
            $config = 1;
        } elseif (1 > intval($config)) {
            throw new HTML_QuickForm2_InvalidArgumentException(
                'Nonempty Rule accepts a positive count of nonempty values, ' .
                preg_replace('/\s+/', ' ', var_export($config, true)) . ' given'
            );
        }
        return parent::setConfig(intval($config));
    }