private function sortingPrefixer(ConfigInterface $config)
    {
        $sorting = [];
        foreach ($config->getSorting() as $property => $value) {
            if (0 === \strpos($property, $this->source . '.')) {
                $sorting[$property] = $value;

                continue;
            }

            if (!$this->fieldExists($property)) {
                continue;
            }

            $sorting[$this->source . '.' . $property] = $value;
        }
        $config->setSorting($sorting);
    }