Wrong gem level displayed on gemcutter interface

When you have +X level of gems as support gems (the mastery supports), the display on the gemcutter interface shows the level of the gem after counting the support/mastery supports and not the base level of the gem.

For reference, my raging spirit's base level is 16 and I'm using an uncut spirit gem 17 (you can see this on the skill but the tooltip here is wrong).
I have confirmed it comes from support gems because whenever I remove the support gems, the tooltip changes (you can make it show 17 > 17)