private function validateDefinitionConfig($name, array &$config)
    {
        if (true === $config['virtual'] && 0 === count($config['property_paths'])) {
            throw new \InvalidArgumentException(sprintf('"property_paths" must be set for "virtual" characteristic "%s".', $name));
        }
        if ($config['type'] === 'datetime') {
            if ($config['format'] === '%s') {
                $config['format'] = 'd/m/Y';
            }
        } elseif (false === strpos($config['format'], '%s')) {
            throw new \InvalidArgumentException(sprintf('"format" must contain "%%s" for characteristic "%s".', $name));
        }
    }