Interface problem in ObjectNormalizer

[ixtensa]

I installed the Bundle (6.0.1) on my project and followed the docs to create a index.
Now I got this error:

Type error: Argument 3 passed to ONGR\ElasticsearchBundle\Mapping\ObjectNormalizer::__construct() must be an instance of Symfony\Component\Serializer\NameConverter\NameConverterInterface or null, instance of ONGR\ElasticsearchBundle\Mapping\NameConverter given, called in /PATH/var/cache/dev/ContainerFq9sxcg/getObjectNormalizerService.php on line 8

I fixed it temporarily by editing /Mapping/NameConverter.php:

use Symfony\Component\Serializer\NameConverter\NameConverterInterface;

class NameConverter implements NameConverterInterface, AdvancedNameConverterInterface