It must actually be:

    override val supervisorStrategy =
      OneForOneStrategy(maxNrOfRetries = 10, withinTimeRange = 1 minute) {
        case _: ArithmeticException ⇒ Resume
        case t ⇒
          super.supervisorStrategy.decider.applyOrElse(t, (_: Any) ⇒ Escalate)
      }

What do you think about making `SupervisorStrategy.escalateDefault` public?