private function validateCustomStylesConfiguration(
        ContainerInterface $container,
        array $enabledCustomStyles
    ) {
        $definedCustomStyles = array_keys(
            $container->getParameter(EzPublishCoreExtension::RICHTEXT_CUSTOM_STYLES_PARAMETER)
        );
        foreach ($enabledCustomStyles as $customStyleName) {
            if (!in_array($customStyleName, $definedCustomStyles)) {
                throw new InvalidConfigurationException(
                    "Unknown RichText Custom Style '{$customStyleName}'"
                );
            }
        }
    }