Can not socket Inhibitor into Spellsinger w/ Ball Lightning

I have a Spellslinger skill from a wand, and I have Ball Lightning socketed in it, and want to add Inhibitor to keep it from using my fire infusions. However, the game doesn't let me do this. I've disabled the gemcutting and equipping restrictions already. The message it shows me when hovering over Spellslinger with the Inhibitor gem is "Warning: - This support can't be socketed into this skill".