Thanks James Pether Sörling for reporting this!
I'll see if we can change these still for 5.8 but can't promise it as I know that - while these are menant to be private API - some strategical projects are still using them.

Please keep in mind that while we've been testing Java9 compatibility extensively, we didn't work on making these proper modules yet: there might be more problems and if significant API changes are necessary these will have to wait for the next release.

Incidentally, this is exactly the kind of problems we've been warning the jigsaw team about. I still hope they will eventually implement proper encapsulation by allowing duplicates among classes which are not exported, as projects need to be able to evolve APIs at independent release cadence.

May I ask how you're defining the modules? Looks like we need to urgently agree at least on stable module names, however I wouldn't want to send mixed signals by suggesting that it's expected to work as a module.