Client Object Model - Unhandled Exception: System.InvalidCastException: Unable to cast object of type 'System.Collections.Generic.Dictionary`2[Syst em.String,System.Object]' to type 'Microsoft.SharePoint.Client.Field'

What is wrong with this code... seems harmless to me.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.SharePoint;
using Microsoft.SharePoint.Client;
namespace ConsoleApplication1 {
    class Program {
        static void Main(string[] args) {
            ClientContext c = new ClientContext("http://sp2013.mycompany.com/sites/dev");
            Web web = c.Web;
            c.Load(web, w => w.Title, w => w.Fields);
            c.ExecuteQuery();
            Console.WriteLine(web.Title);
            FieldCollection collField = web.Fields;
            c.Load(collField, fields => fields.Include(field => field.Title));
            c.ExecuteQuery();
            foreach (Field x in collField) {                               
                Console.WriteLine(x.Title);
            }
        }
    }
}

val it: unit=()