If an exception is thrown from a synchronous `OnSubscribe` it will skip the operators such as `onErrorResumeNext`. For example: ``` java Observable.create(subscriber -> { throw new RuntimeException("failed!"); }).onErrorResumeNext(throwable -> { return Observable.just("fallback value"); }).subscribe(System.out::println, t -> System.out.println("ERROR: " + t.getMessage())); ``` In this case `onErrorResumeNext` is not called and the error passes through.