problem seems to be the modulator check from 7f20635#diff-c00f12e0a2700d71b3ad1b39305d8f2bR21 (likely due return false for when it does not need to set). seems to me the condition logic has a typo - should have been || instead of && ... will shoot up a PR with a test to see what CI thinks.
backport9 v1.3 has been released and I've pushed update_backport9 branch for JRuby. When that's green I'll merge to master and let you take it from there @kares. I had some odd spec:ji failures locally that may mean my environment is dirty.