Entity Framework 6.1.3 Hierarchy id not working

I am trying to use SQL server HierarchyId data type with Entity Framework. Since entity framework doesn't have support for HierarchyId data type I am using Entity Framework fork which has hierarchyid support: https://entityframework.codeplex.com/SourceControl/network/forks/zgabi/EfHierarchyId/latest

DB Table is as follows:

CREATE TABLE OrgStructure(
    [Id] [hierarchyid] NOT NULL,
    [Level]  AS ([Id].[GetLevel]()),
    [NodeId] [int] IDENTITY(1,1) NOT NULL,
    [Title] [varchar](50) NULL)

My Entity which uses HierarchyId data type is defined follows:

public class OrgStructure
{        
    public HierarchyId  Id { get; set; }
    public Nullable<int> Level { get; set; }
    public int NodeId { get; set; }
    public string Title { get; set; }
}

and EntityFramework Mapping configuration is defined as:

public class OrgStructureMapping: EntityTypeConfiguration<OrgStructure>
{
    public OrgStructureMapping()
    {
        // Primary Key
        this.HasKey(t => t.Id);

        // Properties
        this.Property(t => t.Id)
            .HasColumnType("hierarchyId")
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Computed);

        this.Property(t => t.NodeId)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);

        this.Property(t => t.Title)
            .HasMaxLength(50);

        // Table & Column Mappings
        this.ToTable("OrgStructure");
        this.Property(t => t.Id).HasColumnName("Id");
        this.Property(t => t.Level).HasColumnName("Level");
        this.Property(t => t.NodeId).HasColumnName("NodeId");
        this.Property(t => t.Title).HasColumnName("Title");
    }
}

DBContext is as follows:

public partial class VisibilityHierarchyDBContext : DbContext
{

    public virtual DbSet<OrgStructure> OrgStructure { get; set; }

    public VisibilityHierarchyDBContext(string nameOrConnectionString)
    : base(nameOrConnectionString)
    {
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Configurations.Add(new OrgStructureMapping());            
    }
}

Registered DbContext in startup.cs as follows

public void ConfigureServices(IServiceCollection services)
    {
        services.AddScoped<VisibilityHierarchyDBContext>((s) => new VisibilityHierarchyDBContext(Configuration.GetConnectionString("VisibilityDB")));

        // Add framework services.
        services.AddMvc();
    }

Using DBContext as follows:

public class HomeController : Controller
{
    VisibilityHierarchyDBContext context;
    public HomeController(VisibilityHierarchyDBContext context)
    {
        this.context = context;
    }
    public IActionResult Index()
    {
        var o = context.OrgStructure.Take(5).ToList();  /* Exception is  thrown here */

        return View();
    }
 }

I am getting following error in Index action shown above:

The 'Id' property on 'OrgStructure' could not be set to a 'Microsoft.SqlServer.Types.SqlHierarchyId' value. You must set this property to a non-null value of type 'System.Data.Entity.Hierarchy.HierarchyId'.

Any help to resolve this error is much appreciated.