This mod no longer works with 1.12 or 1.12.1. This looks unintentional, so I submitted #40 to fix it in future versions. However, version 1.6.5 on Curse is marked as compatible with these versions despite not actually working on them. You should unmark that release as being compatible with 1.12 and 1.12.1 so that users don't accidentally download it and break their instance.

#40 merged, awaiting next release.