Setting IonTextOptions.Json to true results in invalid JSON

[pbcornell]

The following code

IIonReader reader = IonReaderBuilder.Build("{data: annot::{foo: null.string, bar: (2 + 2)}, time: 1969-07-20T20:18Z}");

TextWriter tw = new StringWriter();
IIonWriter writer = IonTextWriterBuilder.Build(tw, new IonTextOptions {Json = true});
writer.WriteValues(reader);
writer.Finish();
Console.WriteLine(tw.ToString());

produces the following invalid JSON:
{data:annot::{foo:null.string,bar:(2 '+' 2)},time:1969-07-20T20:18:00.0000000+00:00}