How can I resolve conflicting actor systems while testing akka-http and akka actors at the same spec file?

I have a Route defined using akka-http that uses an actor inside to send messages. My route looks like this:

      path("entity") {
        post {
          entity(as[Enrtity]) {
            entity =>
              val result: Future[Message] = mainActor.ask {
                ref: akka.actor.typed.ActorRef[Message] =>
                  Message(
                    entity = entity,
                    replyRef = ref
                  )
              }
              complete("OK")
          }
        }
      }

My test spec:

class APITest
    extends ScalaTestWithActorTestKit(ManualTime.config)
    with ScalatestRouteTest
    with AnyWordSpecLike {
      val manualTime: ManualTime = ManualTime()
     // my tests here ...
}

Compiling the test fails since there are conflicting actor systems:

class APITest inherits conflicting members:
[error]   implicit def system: akka.actor.typed.ActorSystem[Nothing] (defined in class ActorTestKitBase) and
[error]   implicit val system: akka.actor.ActorSystem (defined in trait RouteTest)

Overriding the actor system doesn't help either since the inherited actor systems are of both typed and untyped ones. How can I resolve this easily?