Expose/Mace/Resistance Trooper Question

Res Tro has an ability called Guerilla Tactics in which he gets a buff anytime someone exposes. Mace has a chance to expose at the start of each turn for the duration of his turn.
My question is, when Mace exposes, does that set off Guerilla Tactics, or does expose have to be up during Res Tro's trun?