Rebus: Multiple sagas handling same message -OR- best practice for request/reply in saga

I have a scenario where I'm processing a message in a Saga and might need more information and thus send a request message for which I expect a reply.

The issue is that the reply does not have information unique to the current saga - it has an ID that I would like to use but multiple sagas might be requesting this ID at the same time and thus Rebus disallows it (exception: Correlation property 'Bla' has value '86' in existing saga data with ID 2d12a863-12ed-4632-82d8-290e041c4eed).

If there is no way to have a single message be handled by multiple sagas the alternative for me would be to be able to match the reply to the requesting saga. As far as I can tell there used to be support for this, but it was removed in a later version.

I've tried implementing this using the rbs2-corr-id header, and it works in my tests, however it feels like a hack.

Is there a better way to do it? Without modifying the messages?

I've considered using another saga to act as a sort of proxy by correlating on the ID that might be shared and having a list of correlation IDs for the original saga. I worry however that there might be concurrency issues causing the original saga to wait for the proxy saga.

The following code should show the problem:

public class Message
{
    public Guid Id { get; set; }
    public int OtherId { get; set; }
}

public class Request
{
    public int OtherId { get; set; }
}

public class Response
{
    public int OtherId { get; set; }
    public string MissingInfo { get; set; }
}

public class SagaData : ISagaData
{
    public Guid Id { get; set; }
    public int Revision { get; set; }

    public Guid MessageId { get; set; }
    public int OtherId { get; set; }
}

public class MySaga : Saga<SagaData>, IAmInitiatedBy<Message>, IHandleMessages<Response>
{
    IBus _bus;

    public MySaga(IBus bus)
    {
        _bus = bus;
    }

    public async Task Handle(Message message)
    {
        Data.OtherId = message.OtherId;

        // Send Request expecting someone to .Reply(new Response { OtherId = ,... })
        await _bus.Send(new Request { OtherId = message.OtherId });
    }

    public async Task Handle(Response message)
    {
        // Do something with message.MissingInfo
    }

    protected override void CorrelateMessages(ICorrelationConfig<SagaData> config)
    {
        config.Correlate((Message m) => m.Id, s => s.MessageId);

        // This works as long as only one saga has this ID
        config.Correlate((Response m) => m.OtherId, s => s.OtherId);
    }
}