There is a warning already:
<b>IMPORTANT NOTICE:</b> the actor being terminated and its supervisor
   * being informed of the availability of the deceased actor’s name are two
   * distinct operations, which do not obey any reliable ordering. Especially
   * the following will NOT work:

Await.result(gracefulStop(someChild, timeout), timeout)
   *     context.actorOf(Props(...), "someChild") // assuming that that was someChild’s name, this will NOT work