WhenSessionChanged seems to not working as LocalSystem

Question

I have created windows service with TopShelf:

HostFactory.Run(x =>
{
    x.UseAutofacContainer(BuildScope());

    x.Service<BootstrapService>(s =>
    {
        s.ConstructUsingAutofacContainer();
        s.WhenStarted(tc => tc.Start());
        s.WhenStopped(tc => tc.Stop());
        s.WhenSessionChanged((bs, args) => bs.SessionChanged(args));
    });

    x.RunAsLocalSystem();

    x.SetDescription(CONST_Description);
    x.SetDisplayName(CONST_DisplayName);
    x.SetServiceName(CONST_ServiceName);
});

Service is running as LocalSystem. The problem is that when other user logs into windwos, WhenSessionChanged is not called. Why and how can I make this callback to work?