IndentedTextWriter Async Fail

Program.cs

using System.CodeDom.Compiler;
using System.IO;
using System.Text;
using System.Threading.Tasks;

namespace IndentFail
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var sb = new StringBuilder();
            var sw = new StringWriter(sb);
            var tw = new IndentedTextWriter(sw);

            tw.Indent++;

            await tw.WriteLineAsync("Foo");
            await tw.WriteLineAsync("Bar");
            await tw.WriteLineAsync();
            await tw.WriteLineAsync("Quux");
            await tw.WriteLineAsync("Wibble");

            System.Console.WriteLine(sb.ToString());
        }
    }
}

Result.txt

Foo
    Bar

Quux
    Wibble