Is there a known bug for bernard.receiver when used with symfony 4?

I tried using bernard-bundle in my Symfony 4.3 project to run a basic helloWorld background task, but when I try to run bernard: consume I get an error

In SimpleRouter.php line 38:

Given "my_receiver" is not supported. 

This is the services.yaml part

 my_receiver:
        class: App\BackgroundTasks\Receiver\
        tags:
            - { name: bernard.receiver, message: 'HelloWorld' }

It says the error is in SimpleRouter, so I tried debugging there using

    var_dump($name);
    var_dump($receiver);
    var_dump(class_exists($receiver)); 

and I got

    string(10) "HelloWorld"
    string(11) "my_receiver"
    bool(false)

Is this a bug because of Symfony? Or am I missing something?