Obj-C: Getting "over quota" error after session start for uploading chunks

Whenever an API call fails, I like to check to see if the user is over their usage quota, and if so, I throw up a warning that they need to delete some files or upgrade their Dropbox account. As Greg previously explained, I can do this using the route error passed into the response methods, e.g.:

DBFILESUploadError *routeError = ...

if (routeError.isPath && routeError.path.isInsufficientSpace)
    NSLog (@"Update your Dropbox account or tidy up!");

However, there seems to be no way to do this after calling DBFILESRoutes -uploadSessionStartData:, because the callback for this method does not return a route error. Instead, it provides a DBNilObject object where the route error would normally be. So how do I check for "over quota" (isInsuffientSpace) error in this case?

Can I check the statusCode of the DBError? (In API 1, a 507 indicated that you were out of space, for instance.)

Thanks and all the best,
Keith