Creating a TestActorRef throws a NullPointerException

I am trying to get the same TestActorRef

class NotifySenderTest(_system: ActorSystem) extends TestKit(_system) with ImplicitSender with WordSpecLike with Matchers with BeforeAndAfterAll with BeforeAndAfter {

  def this() = this(ActorSystem("NotifySenderTest"))
  override def afterAll {
    TestKit.shutdownActorSystem(system)
  }

  "A NotifySender" must {
    "be able to process the required messages" in {
      val actorRef = TestActorRef[NotifySender] //Line 92
    }
  }

this actor

class NotifySender extends Actor with Stash {
  import Tcp._
  import context.system

  def receive = {
  [...]
  }
}

But that leaves me with the next stacktrace

java.lang.NullPointerException: akka.actor.dungeon.Dispatch $class.init(Dispatch.scala: 62) . akka.actor.LocalActorRef. (ActorRef.scala: 304) at akka.testkit.TestActorRef. (TestActorRef.scala: 21) at akka.testkit.TestActorRef $.apply(TestActorRef.scala: 141) at akka.testkit.TestActorRef $.apply(TestActorRef.scala: 137) at akka.testkit.TestActorRef $.apply(TestActorRef.scala: 146) at akka.testkit.TestActorRef $.apply(TestActorRef.scala: 144) at actor.NotifySenderTest $$ anonfun $2 $$ anonfun $ $ $ $4.Apply $ $ (NotifySenderTest.scala: 92) actor.NotifySenderTest $$ anonfun $2 $$ anonfun $ $MCV $ $4.Apply(NotifySenderTest.scala: 91)...

: , - . TestActorRef . , TextActorRefs , Stash, , , . ()

Edit2: . . 2.3. ?!