Akka asks onComplete to call twice

Question

I have an actor who asks another actor with a timeout.

Sometimes onComplete onReceive handlers are called twice. The last call is AskTimeout, the first call that I have not had debugging or registration yet.

I can not find any documents that explicitly say that onComplete should be called only once. Are multiple calls expected or an error?

I am using Java 1.6, Akka 2.1.1 and Scala library 2.10.0