Wrong media type for built-in byte[]/stream codec

[JornWildt]

When posting a stream like this:

using (Stream sData = File.OpenRead(filePath))
using (var response = session.Bind(url).Post(sData))
{
}

It sends / as the media type. Thats not a valid type.

But what would be the right? In my exact case it would be "zip" - but the default should probably be "binary".