Flex :: Uploading Bytearray Via URLRequest?

I'm trying to upload a bytearray, but am struggling to make the content-type go as image/png (it always goes as application/octet-stream no matter what I do.).I've checked the request with Charles Proxy, and can confirm that it indeed always goes as application/octet-stream.My code is:

protected function onObjectLoaded(event:Event):void
{
var byteArray:ByteArray = new ByteArray();
var fileName:String = fileReference.name;
var uploadPath:String = serviceURL;

[code]....

how to change this, so the bytearray itself gets passed in as image/png instead of octet-stream This image is being upload from the client side, and being passed as a FileReference, which I then invoke load(), and then get it's "data" attribute, which is where the bytearray is.