[jvm-packages] error using a custom evaluation function (setCustomEval) on spark

I am trying to use a custom evaluation function (setCustomEval) on spark. However, it is giving the following error:

[ERROR] [08/16/2018 13:34:42.313] [RabitTracker-akka.actor.default-dispatcher-11] [LocalActorRefProvider(akka://RabitTracker)] guardian failed, shutting down system
java.lang.AssertionError: assertion failed
at scala.Predef$.assert(Predef.scala:156)
at ml.dmlc.xgboost4j.scala.rabit.handler.WorkerDependencyResolver$$anonfun$receive$2.applyOrElse(RabitTrackerHandler.scala:298)
at akka.actor.Actor$class.aroundReceive(Actor.scala:467)
at ml.dmlc.xgboost4j.scala.rabit.handler.WorkerDependencyResolver.aroundReceive(RabitTrackerHandler.scala:264)
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
at akka.actor.ActorCell.invoke(ActorCell.scala:487)
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:238)
at akka.dispatch.Mailbox.run(Mailbox.scala:220)
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)