AC Oulu's goalless draw with league leaders Inter Turku at the weekend opened the door for KuPS to move second with victory on Wednesday, but a positive response from Oulu sees them climb back into second, now only a point behind FC Inter after they threw away the lead against HJK.
The chance to edge closer to the frontrunners looked to be passing the home side down, as after a goalless first half, a shock was on the cards when Mariehamn took the lead on 65 minutes. Luke Pearce cut inside from the left and fed the ball across for Marlo Hyvonen to turn home on the stretch.
But the advantage lasted just 11 minutes, as Rasmus Karjalainen found Julius Korkko, who levelled for Oulu with his fifth league goal of the season.
The visitors looked to have done enough to hold on for an unlikely point, only for Oulu to save their Midsummer celebrations with a 93rd-minute winner - Korkko turned provider, clipping a free-kick into the box where Abdoulaye Kone climbed highest to nod home.
It's four wins and a draw in their last five now for Oulu, while the Aland Islanders have lost four in a row and still without a win from their 11 league matches.