How to restrict actor messages to specific types?

In Akka, is there a way to restrict messages to actors to be of a specific static type other than using the "Typed Actor" APIs that use an RPC style programming model?

Can I use the message passing style with Akka without throwing away static type safety at the actor boundaries?

For example, I'd like to use code like this:

sealed abstract class FooMessage
case object Foo extends FooMessage
case object Bar extends FooMessage

class FooActor extends Actor[FooMessage] {
  def receive = {
    case Foo => () // OK

    // Would raise a compiler error:
    // case s: String => error("Can't happen, String is not a subtype of FooMessage") 

  }
}

val fooActor = actorOf[FooActor]
fooActor ! Foo // OK

// Won't compile:
fooActor ! "Hello"

Perhaps one would have to extend some base trait or have a construct like Either to allow for system level messages (Exit, etc.).