Support #HystrixCommand for rx.Observable - hystrix

Question

I am trying to use #hystrixcommand with rx.Observable. Below is the code snippet.
Issue is the timeout setting on the Hystrix property seems not working, it is not calling the fall back method after 10 sec time out, please help.
#HystrixCommand(fallbackMethod = "assignActionsToUserFallback", commandProperties = {
#HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "10000")})
public Observable<Void> assignActionsToUser(List<String> actions, String newUserId, Date startTime,
Date endTime, String lastUpdUserId) {
return Observable.fromCallable(() -> {
_log.info("HystrixObservableUtil :: Assign actions to user start");
externalUserManagementService.assignActionsToUser(actions, newUserId, startTime, endTime, lastUpdUserId);
_log.info("HystrixObservableUtil :: Assign actions to user end");
return null;
});
}
private void assignActionsToUserFallback(List<String> actions, String newUserId, Date startTime,
Date endTime, String lastUpdUserId) {
System.out.println("Error........");
}
Caller -
Observable<Void> assignUserActionObservable = hystrixObservableUtil.assignActionsToUser(
actions, newUserId, start.getTime(), end.getTime(), "EXTTMS").subscribeOn(Schedulers.io());