Doctrine Mapped Superclass index column ID not found on child table?

Question

Doctrine ORM

<mapped-superclass name="App\Domain\Token\Entity\AbstractToken">
        <embedded name="id" class="App\Domain\Core\ValueObjects\EntityId" use-column-prefix="false"/>
        <embedded name="secret" class="App\Domain\Token\ValueObject\TokenSecret" use-column-prefix="false"/>
// ok
...
  <entity name="App\Domain\Token\Entity\AnonToken">
        <indexes>
            <index name="token_search_index" columns="id,secret"/>
        </indexes>
    </entity>

If you remove the ID from the index, then the mapping is working.

class AbstractToken implements IAggregateRoot {
    public EntityId                      $id;
    private TokenSecret                     $secret;

It doesn't matter where I put the index, in mapped-superclass mapping or child mapping, it shows that the ID is not found, but sees the secret for the index, why?