WebApi Put «Словарь параметров содержит нулевую запись для параметра…»

public class ContactsController : ApiController
{
    private static readonly List<Contact> _contacts = new List<Contact>();
    public Contact PutContacts(int id, Contact contact)
    {
        if (_contacts.Any(c => c.Id == contact.Id) == false)
        {
            throw new HttpResponseException(HttpStatusCode.NotFound);
        }
        contact.LastModified = DateTime.Now;
        return contact;
    }
}

http put header:

PUT /api/contacts/3 HTTP/1.1
User-Agent: Fiddler
Content-Type: application/json
Host: localhost:8080

body:

{"Id":3,"Name":"mmm","Phone":"000 000 0000","Email":"mmm@gmail.com","LastModified":"2012-03-08T23:42:13.8681395+08:00"}

response:

HTTP/1.1 400 Bad Request
"The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32' for method 'SelfHost.Contact PutContacts(Int32, SelfHost.Contact)' in 'SelfHost.ContactsController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter."

Почему? благодаря.

ПС:

config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );