ETag header not sent

We’re trying to set the etag header in a worker like this:

    const headers = new Headers();
    headers.set('ETag', 'test');

    return new Response('test', {            

but it doesn’t reach the client. Is there a list of approved headers that you can send from the worker?

Found this post about that only week ETags are supported by default:

When changing to use weak etags it works just fine from the worker.