jrebel 404 for index.yml

I am trying to build a java-buildpack with bundle exec rake PINNED=true OFFLINE=true

…but it throws:

WARN Unable to download https://dl.zeroturnaround.com/jrebel/index.yml into cache build/staging/resources/cache: 404 Not Found

The file does, in fact, not appear to be there. Was this moved? Do I need to grab a later version of the java buildpack from github.com, or is this something I was meant to ignore but jrebel will work?