The code below compiles and runs fine when timeout is given its value inside the ParentActor abstract class.
However, if timeout is abstract in the ParentActor and only defined in the MyActor class as below, then I get a rather cryptic "akka.actor.ActorInitializationException: exception during creation".

Scala 2.10.3, Akka 2.3.1.

object Error extends App {
  val system = ActorSystem("test")
  system.actorOf(Props(classOf[MyActor]), "my-actor")
}

class MyActor extends ParentActor {
  val timeout: FiniteDuration = 20.milliseconds

  def receive: Receive = {
    case Hello => println("hello")
  }
}

abstract class ParentActor extends Actor {
  val timeout: FiniteDuration

  import context.dispatcher
  context.system.scheduler.scheduleOnce(timeout) {
    self ! Hello
  }
}

case object Hello

[ERROR] [04/08/2014 17:56:25.486] [test-akka.actor.default-dispatcher-3] [akka://test/user/my-actor] null
akka.actor.ActorInitializationException: exception during creation
	at akka.actor.ActorInitializationException$.apply(Actor.scala:164)
	at akka.actor.ActorCell.create(ActorCell.scala:596)
	at akka.actor.ActorCell.invokeAll$1(ActorCell.scala:456)
	at akka.actor.ActorCell.systemInvoke(ActorCell.scala:478)
	at akka.dispatch.Mailbox.processAllSystemMessages(Mailbox.scala:263)
	at akka.dispatch.Mailbox.run(Mailbox.scala:219)
	at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:393)
	at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
	at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
	at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
	at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
Caused by: java.lang.NullPointerException
	at akka.actor.LightArrayRevolverScheduler.akka$actor$LightArrayRevolverScheduler$$roundUp(Scheduler.scala:204)
	at akka.actor.LightArrayRevolverScheduler.scheduleOnce(Scheduler.scala:275)
	at akka.actor.Scheduler$class.scheduleOnce(Scheduler.scala:117)
	at akka.actor.LightArrayRevolverScheduler.scheduleOnce(Scheduler.scala:182)
	at demo.ParentActor.<init>(Error.scala:23)
	at demo.MyActor.<init>(Error.scala:11)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at java.lang.Class.newInstance(Class.java:374)
	at akka.util.Reflect$.instantiate(Reflect.scala:45)
	at akka.actor.NoArgsReflectConstructor.produce(Props.scala:358)
	at akka.actor.Props.newActor(Props.scala:249)
	at akka.actor.ActorCell.newActor(ActorCell.scala:552)
	at akka.actor.ActorCell.create(ActorCell.scala:578)
	... 9 more