I've done some digging around because that -115 sounded familar to me and this issue comes up a few times but I find it never gets completely resolved.
Your class file looks fine and I can process it no problem. So there is something else going on.
I would like to get to the bottom of it but I suspect as it is something subtle I'll need to recreate - is there any way you can share your app with me? (privately email it to me?) I have STS/etc all ready to go.