return waitFor(closingCallable, ClosingCallable.class);
    }

    @SuppressWarnings("unchecked") // proxy for a generic class
    <V> AsyncClosingCallable<V> waitFor(AsyncClosingCallable<V> asyncClosingCallable) {
      return waitFor(asyncClosingCallable, AsyncClosingCallable.class);
    }

    @SuppressWarnings("unchecked") // proxy for a generic class