public function checkProperty(&$property)
    {
        if (parent::checkProperty($property)) {
            if (preg_match(
                '/^(?:src|unicode-range|font-(?:family|variant|feature-settings|stretch|weight|style))$/D',
                $property)) {
                return true;
            } else {
                $this->setIsValid(false);
                $this->addValidationError("Invalid property '$property' for @font-face declaration.");
            }
        }

        return false;
    }