I'm not sure that modifying the singleton class will work in Jruby 9k+ - I think they disabled that for performance reasons which we'll also have lots of fun with in our test suite.

However there are ways to re- enable this: https://github.com/jruby/jruby/wiki/Persistence

Just as a FYI won't have to fix that know but we could (it should actually yield warnings if we're affected so maybe I'm just remembering it wrong)