Use an entity class for users

Hi.

I work with my own entities created in code with hook_entity_info(). I have a base class, that inherits from Entity, common with all my entities. I also want that the user entity inherits from my base class.

function webappm_entity_info_alter(&$entity_info) {
  $entity_info['user']['entity class'] = '\Drupal\webappm\Entity\BaseEntity';
}

But when I load an user entity with entity_load() it class is stdClass as usual.

I'm doing something wrong or it isn't possible to do this?

Best regards.