How to authorize users from a parent Windows Domain in ASP.NET MVC application, which is hosted in a child Windows Domain?

I have an ASP.NET MVC 5 web application. It is hosted on IIS 8.5 on Windows Server 2012 R2 in an intranet environment. It uses Windows authentication and authorization.
There is a Windows Domain in the environment: MainDomain. In this domain there is an group of users AppUsers (MainDomain\AppUsers), which is used to authorize users upon accessing the web application's resources.
The web application itself is being hosted under a child Windows Domain ChildDomain (ChildDomain.MainDomain).
I use role-based authorization in the code of my controllers. It looks like this:
[Authorize(Roles = @"MainDomain\AppUsers")] public HomeController : Controller { // Action methods and other stuff... } I've run into a problem: every request (to any act ...