Order Property in MessageBodyMember not working in CoreWCF

Question

I am using CoreWCF in one of my .NET Core project. I have following contract. Everything works fine, but the Order property on MessageBodyMember is not honoured. The order of elements are always alphabetical. What could be the issue?

using CoreWCF;

[MessageContract]
public class User
{
    [MessageBodyMember(Order = 1)]
    public DateTime now { get; set; }
    [MessageBodyMember(Order = 2)]
    public string company { get; set; }
    [MessageBodyMember(Order = 3)]
    public string login { get; set; }
    [MessageBodyMember(Order = 4)]
    public string auth_string { get; set; }
}