Is ok, obvious answer ........ but ......
Given the novelty of this upgrade, especially for the lower consumption of resources, it would be necessary to get to a compatible version of Forge.
Today it stops at 1.9, skip the 1.9.1 and 1.9.2 .......
Lex said in another thread that 1.9.1/1.9.2 mostly changed hard coded values to enums, and as such there wasn't any reason to release those versions. I expect 1.9.4 is different, and you can check the diff log on github to know for sure.