Repeatedly subscribe to a Mono using repeatWhen() and takeUntil()

Question

I am trying to understand the effect of repeatedly subscribe to a Mono with a delay of 1 second and stop subscribing based on a certain condition, I have this line of code

     Mono.just(UUID.randomUUID())
            .map(uuid -> uuid.toString())
            .doOnNext(uuid -> System.out.println(uuid))
            .repeatWhen(completed -> completed.delayElements(Duration.ofMillis(1000)))
            .takeUntil(uuid -> uuid.startsWith("1234"))
            .subscribe();

What I expect from that line, is to keep printing a random UUID every one second, until it generate one starting with 1234 and then stop. But it just print just on UUID and then exits. How do I achieve that using this line ?