ASP.NET MVC redirect to an access denied page using a custom role provider

[AccessDeniedAuthorize(Roles="SuperAdmin")]
public class SuperAdminController : Controller

AccessDeniedAuthorizeAttribute.cs:

public class AccessDeniedAuthorizeAttribute : AuthorizeAttribute
{
    public override void OnAuthorization(AuthorizationContext filterContext)
    {
        base.OnAuthorization(filterContext);

        if(filterContext.Result is HttpUnauthorizedResult)
        {
            filterContext.Result = new RedirectResult("~/AcessDenied.aspx");
        }
    }
}