While KuPS had seen Inter Turku replace them at the top of the table earlier this weekend, their draw with HJK gave the Kuopio side the incentive to open a gap between them and the chasing pack.
But that would be easier said than done against an SJK side who had won four in a row and three points off the top themselves at kick-off.
Though the hosts had only one shot on target of the first half, it was the best chance of the first 45 minutes, but Kasper Paananen was denied by Johannes Kreidl.
At the other end, Doni Arifi and Agon Sadiku looked particularly lively for the visitors, but it looked as though the breakthrough would never come and KuPS would have to settle to going one points clear again.
That was until the 90th minute, when a KuPS corner to the back post was met by Samuel Chukwudi, who got his attempted clearing header all wrong, and placed the ball into the back of his own net to hand KuPS a 1-0 win.
It was a touch of very good fortune for KuPS, whose unbeaten league run stretches to six games, and next up they face Gnistan, who have nothing to play for.
The own goal has severely dented SJK's title challenge, who are now six points off the new leaders with three matches to play, and are two points behind Ilves, who occupy the final European place.