Scheduler.Worker thread. Add `onError` handling. at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:60) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Caused by: rx.exceptions.OnErrorNotImplementedException: Sequence contains no elements at rx.Observable$26.onError(Observable.java:7881) at rx.observers.SafeSubscriber._onError(SafeSubscriber.java:159) at rx.observers.SafeSubscriber.onError(SafeSubscriber.java:120) at rx.internal.operators.OperatorSubscribeOn$1$1$1.onError(OperatorSubscribeOn.java:71) at rx.internal.operators.OperatorSingle$ParentSubscriber.onCompleted(OperatorSingle.java:131) at rx.internal.operators.OperatorTake$1.onCompleted(OperatorTake.java:53) at rx.Observable$EmptyHolder$1.call(Observable.java:1073) at rx.Observable$EmptyHolder$1.call(Observable.java:1070) at rx.Observable$2.call(Observable.java:162) at rx.Observable$2.call(Observable.java:154) at rx.Observable$2.call(Observable.java:162) at rx.Observable$2.call(Observable.java:154) at rx.Observable.unsafeSubscribe(Observable.java:8098) at rx.internal.operators.OperatorSubscribeOn$1$1.call(OperatorSubscribeOn.java:62) at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55) ... 7 more Caused by: java.util.NoSuchElementException: Sequence contains no elements ... 18 more No references to my code!