Masstransit UseInMemoryOutbox not working with MultiBus Saga?

Question

I implemented a custom activity for supporting multibus saga. But I found an issue that is I received a published message from SecondBus before the state saga saves to Redis. I think UseInMemoryOutbox() should handle this or i wrong.

public class TestActivity : Activity<SagaState, IFirstBusRequest>
{
    private readonly ISecondBus _secondBus;

    public TestActivity(ISecondBus secondBus)
    {
        _secondBus = secondBus;
    }


    public async Task Execute(BehaviorContext<SagaState, IFirstBusRequest> context, Behavior<SagaState, IFirstBusRequest> next)
    {
        var endpoint = await _secondBus.GetSendEndpoint(new Uri($"queue:second-bus-request"));
        await endpoint.Send(new { }); // send immediately
    }      
}