Entity Framework CTP5 - Code First - Nested Query Error

I have the following classes:

public class Category
{
public int CategoryId { get; set; }
public string Name { get; set; }
}
public partial class CategoryMap : EntityTypeConfiguration<Category>
{
public CategoryMap()
{
this.HasKey(c => c.CategoryId);
this.Property(c => c.Name).IsRequired().HasMaxLength(400);
}
}
public class MyObjectContext : DbContext
{
public MyObjectContext(string connectionStringName)
: base(connectionStringName)
{
}
public DbSet<Category> Categories { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Configurations.Add(new CategoryMap());
base.OnModelCreating(modelBuilder);
}
}

Now when I run the following code I get an exception (GenericArguments[0], 'System.Int32', on 'System.Data.Entity.Internal.Linq.ReplacementDbQueryWrapper`1[TEntity]' violates the constraint of type 'TEntity')

DbDatabase.SetInitializer<MyObjectContext>(new DropCreateDatabaseIfModelChanges<MyObjectContext>());
using (var context = new MyObjectContext("NopSqlConnection"))
{
var query1 = from c in context.Categories
select c.CategoryId;
var test1 = query1.ToList(); //works fine
var query2 = from c in context.Categories
where query1.Contains(c.CategoryId)
orderby c.Name descending
select c;
var test2 = query2.ToList(); //throws the exception
}