.net - I can't get the callscope of my session to work

Question

I'm having trouble scoping my IDocumentSession dependency with Ninject.

Every time my bus executes a command, I want a new IDocumentSession. Commandhandlers that are created by the factory should have that same instance of IDocumentSession injected. I thought putting the bus in a CallScope would work, but I think the AsFactory breaks the CallScope? How would I get this done?

public class Bus : IBus
{
    private readonly ICommandHandlerFactory _factory;
    private readonly IDocumentSession _session;

    public Bus(ICommandHandlerFactory factory, IDocumentSession session)
    {
        _factory = factory;
        _session = session;
    }

    public void ExecuteCommand<T>(T command) where T : class
    {
        var handler = _factory.Create<T>();

        handler.Handle(command);

        _session.SaveChanges();
    }
}

public class ActivateAccountCommandHandler : ICommandHandler<ActivateAccountCommand>
{
    private readonly IDocumentSession _session;

    public ActivateAccountCommandHandler(IDocumentSession session)
    {   
        _session = session;
    }

    public void Handle(ActivateAccountCommand command)
    {
        // Do something
    }
}

kernel.Bind<IDocumentStore>().ToMethod(ctx => DocumentStore.Get()).InSingletonScope();
kernel.Bind<IDocumentSession>().ToMethod(ctx => ctx.Kernel.Get<IDocumentStore>().OpenSession());

kernel.Bind<ICommandHandlerFactory>().AsFactory();

kernel.Bind<IBus>().To<Bus>().InCallScope();

I also tried with context preservation but this makes no difference.

kernel.Bind<IDocumentSession>().ToMethod(ctx => ctx.ContextPreservingGet<IDocumentStore>().OpenSession());