Compton dimming inactive doesn't work with terminal

Running i3 on ubuntu, with compton (all recent installations). I want to use compton to dim inactive windows. It is currently mostly working using inactive-dim = 0.2 just fine. The problem is that when I run a couple of terminals on the same screen, they're either all dim or all bright - it doesn't dim the terminals that aren't active. I imagine this has something to do with how compton figures out if something is active or not - I can run multiple chrome windows or atom windows or whatever, and those work just fine. Any advice about configuring the terminal launcher? (currently just using i3-sensible-terminal which is launching gnome-terminal).