How to configure Gedmo Sluggable in Symfony 4 properly?

Question

I have tried to configure Gedmo Sluggable properly in a Symfony 4 application and failed. The issue is: it is not working. Any sluggable columns aren't recognized as being sluggable and stay empty after persisting.

composer.json:

"gedmo/doctrine-extensions": "^2.4",

services.yml:

services:
    gedmo.listener.sluggable:
        class: Gedmo\Sluggable\SluggableListener
        tags:
            - { name: doctrine.event_subscriber, connection: default, priority: 1 }
        calls:
            - [ setAnnotationReader, [ '@annotation_reader' ] ]

Entity Faculty.orm.yml:

AppBundle\Entity\Faculty:
    type: entity
    table: faculty
    repositoryClass: AppBundle\Repository\FacultyRepository
    id:
      id:
        type: bigint
        generator:
          strategy: AUTO
    fields:
      name:
        type: string
        column: name
        nullable: false
        length: 128
      slug:
        type: string
        length: 128
        gedmo:
          slug:
            separator: _
            style: camel
            updatable: false
            fields:
              - name
    uniqueConstraints:
        idx_name:
          columns: [ name ]
        idx_slug:
          columns: [ slug ]

However, when i persist an entity, the slug stays empty:

    $faculty = new Faculty();
    $faculty->setName('foobar');

    $this->entityManager->persist($faculty);
    $this->entityManager->flush();

Did i missed something?

I also tried out the StofDoctrineExtensionsBundle following this article. Without any luck. The Sluggable-Listener gets not triggered.