Cache loses content type.

code

using System;
using System.Net;
using System.Net.Cache;
using System.Net.Http;
using System.Threading.Tasks;

namespace HttpCacheTest
{
    class Program
    {
        const string url = "http://<redacted>/octopus/api/projects/projects-<redacted>";
        const string apiKey = "<redacted>";

        static void Main(string[] args)
        {
            DefaultTest().Wait();
            Task.Delay(1000).Wait();
            CachingTest().Wait();
        }

        static async Task DefaultTest()
        {
            Console.WriteLine("Default:");
            using (var httpClient = new HttpClient()
            {
                DefaultRequestHeaders = {
                    { "X-Octopus-ApiKey", apiKey}
                }
            })
            {
                using (var response = await httpClient.GetAsync(url))
                {
                    Console.WriteLine($"{response.Content.Headers.ContentType}");
                }

                await Task.Delay(1000);

                using (var response = await httpClient.GetAsync(url))
                {
                    Console.WriteLine($"{response.Content.Headers.ContentType}");
                }
            }
        }

        static async Task CachingTest()
        {

            Console.WriteLine("With Cache:");
            using (var httpClient = new HttpClient(new WebRequestHandler()
            {
                CachePolicy = new RequestCachePolicy(RequestCacheLevel.Default)
            })
            {
                DefaultRequestHeaders = {
                    { "X-Octopus-ApiKey", apiKey}
                }
            })
            {
                using (var response = await httpClient.GetAsync(url))
                {
                    Console.WriteLine($"{response.Content.Headers.ContentType}");
                }

                await Task.Delay(1000);

                using (var response = await httpClient.GetAsync(url))
                {
                    Console.WriteLine($"{response.Content.Headers.ContentType}");
                }
            }
        }
    }
}

console

Default:
application/json; charset=utf-8
application/json; charset=utf-8
With Cache:
application/json; charset=utf-8
text/plain
Press any key to continue . . .

fiddler

#	Result	Protocol	Host	URL	Body	Caching	Content-Type	Process	Comments	Custom	
1	200	HTTP	<redacted>	/octopus/api/projects/<redacted>	1,379	must-revalidate; Expires: Tue, 05 May 2015 03:18:10 GMT	application/json; charset=utf-8	httpcachetest.vshost:3228			
2	200	HTTP	<redacted>	/octopus/api/projects/<redacted>	1,379	must-revalidate; Expires: Tue, 05 May 2015 03:18:11 GMT	application/json; charset=utf-8	httpcachetest.vshost:3228			
3	200	HTTP	<redacted>	/octopus/api/projects/<redacted>	1,379	must-revalidate; Expires: Tue, 05 May 2015 03:18:13 GMT	application/json; charset=utf-8	httpcachetest.vshost:3228			
4	304	HTTP	<redacted>	/octopus/api/projects/<redacted>	0	no-cache; Expires: Tue, 05 May 2015 03:18:14 GMT	text/plain	httpcachetest.vshost:3228