Issue with Refit JsonConverter

MainActivity.cs

using System;
using System.Globalization;
using System.Threading.Tasks;
using Android.App;
using Android.Widget;
using Android.OS;
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;
using Refit;

namespace RefitJsonConverterIssue
{
	public interface ISomeApiService
	{
		[Get ("/test/something1/")]
		Task<SomeResult> GetParamAttribConverterResult ([JsonConverter (typeof(SomeDateTimeConverter))]DateTime someDate);

		[Get ("/test/something2/")]
		Task<SomeResult> GetJsonConvertDefaultResult (DateTime someDate);
	}

	[Activity (Label = "RefitJsonConverterIssue", MainLauncher = true, Icon = "@drawable/icon")]
	public class MainActivity : Activity
	{
		int count = 1;

		protected override void OnCreate (Bundle bundle)
		{
			base.OnCreate (bundle);

			JsonConvert.DefaultSettings = 
				() => new JsonSerializerSettings () { 
				Converters = {
					new SomeDateTimeConverter ()
				}
			};

			var testDate = new DateTime (2014, 11, 7, 16, 32, 54);
			string testDateJson = JsonConvert.SerializeObject (testDate);
			System.Diagnostics.Debug.Assert (testDateJson == "2014-11-07 16:32:54");

			// Set our view from the "main" layout resource
			SetContentView (Resource.Layout.Main);

			// Get our button from the layout resource,
			// and attach an event to it
			Button button = FindViewById<Button> (Resource.Id.myButton);

			var service = RestService.For<ISomeApiService> ("https://yourapihere-com-{yourrunscopebucketid}.runscope.net/");
			button.Click += delegate {
				Task.Run (async () => {
					// NOTE: these all fail since the API doesn't exist. Done just to see outbound URLs in Runscope.
					try {
						var paramAttributeResult = await service.GetParamAttribConverterResult (testDate);
					} catch (Exception ex) {
						Console.WriteLine ("expected fail 1");
					}
					try {
						var defaultConverterResult = await service.GetJsonConvertDefaultResult (testDate);
					} catch (Exception ex) {
						Console.WriteLine ("expected fail 1");
					}
					RunOnUiThread (() => {
						button.Text = string.Format ("{0} clicks!", count++);
					});
				});
			};
		}
	}

	public class SomeResult
	{
		public string SomeString { get; set; }

		public DateTime SomeDate { get; set; }
	}

	public class SomeDateTimeConverter : DateTimeConverterBase
	{
		const string dateTimeFormat = "yyyy-MM-yy HH:mm:ss";

		public override void WriteJson (Newtonsoft.Json.JsonWriter writer, object value, Newtonsoft.Json.JsonSerializer serializer)
		{
			string output;
			if (value is DateTime) {
				output = ((DateTime)value).ToString (dateTimeFormat);
			} else {
				throw new Exception ("Expected date object value.");
			}
			writer.WriteValue (output);
		}

		public override object ReadJson (Newtonsoft.Json.JsonReader reader, Type objectType, object existingValue, Newtonsoft.Json.JsonSerializer serializer)
		{
			if (reader.TokenType != JsonToken.String) {
				throw new Exception (string.Format ("Unexpected token parsing date. Expected string, got {0}.", reader.TokenType));
			}

			DateTime date;
			bool success = DateTime.TryParseExact ((string)reader.Value, dateTimeFormat, CultureInfo.InvariantCulture, DateTimeStyles.None, out date);

			if (!success) {
				throw new Exception ("Invalid date format.");
			}

			return date;
		}
	}
}