St Mirren were beaten at The Tony Macaroni Arena with a Tete Yengi goal enough to give Livingston the three points.
It was a frustrating afternoon for Saints who dominated possession, had 21 shots to Livingston's six and would miss a late penalty after a VAR intervention.
Hyeokkyu Kwon returned to the starting eleven in place of Keanu Baccus while James Scott started ahead of Lewis Jamieson in the only changes from Sunday's Scottish Cup loss to Celtic. Alex Gogic and Greg Kiltie both made it despite being doubtful.
Saints started the game brightly, but it was the hosts who came closest in the first 20 minutes when Andrew Shinnie's header came off the post, though the offside flag was raised.
Kiltie sent an effort over the bar from 20 yards on 22 minutes, while Stephen Kelly saw a powerful shot from distance pushed away by Zach Hemming.
Caolan Boyd-Munce threatened twice from long-range with his first effort saved by Shamal George. The ball broke out to James Scott who knocked over from close-range but the offside flag was raised so it wouldn't have couldn't had he scored. Boyd-Munce was close again in the final minute of normal time in the first-half with his low strike from distance went inches by the post.
The hosts would take the lead when Yengi put them ahead in first-half stoppage time. Ayo Obileye's initial shot from a corner was pushed away by Hemming but the goalkeeper couldn't hold which allowed Yengi to slam home on the follow up.
The manager made a change at the break with Jamieson replacing Scott and the 21-year-old almost made an instant impact when he got on to a loose back pass. He attempted to round the goalkeeper but the ball came back out to Mikael Mandron who laid off for Kiltie on the edge of the area. The forward curled towards the top corner but his effort was headed clear by Michael Nottingham.
Saints were having all the pressure as they looked for a leveller, forcing a succession of corners after the hour mark but failing to make George work in the Livingston goal. Kwon side-footed wide from just inside the area.
The Buddies made two changes with just over 20 minutes remaining as Baccus and Toyosi Olusanya on for Kwon and Kiltie.
And it was Olusanya who looked like he might have helped find Saints a route into the match when he was fouled in the box by David Carson. Referee Euan Anderson didn't give it initially but after a lengthy VAR check the whistler was advised to check the screen where he ended up pointing to the spot. Mandron took the ball but saw his spot-kick saved by George.
The hosts almost doubled their advantage immediately after the penalty miss when a quick free-kick from Zach Hemming was pounced upon by Stephen Kelly who launched wide from 35 yards with the goal gaping.
Mandron had a huge chance to grab a point in the final minutes when slid in at the far post to meet a Jamieson cross but he sent the effort the wrong side of the post.
Full-Time: Livingston 1-0 St Mirren
St Mirren: Hemming, Fraser (c), Gogic, Dunne, Bwomono (Brown 83), Kwon (Baccus 69), Boyd-Munce, Tanser, Kiltie (Olusanya 69), Mandron, Scott (Jamieson 46)
Subs Not Used: Urminsky, Taylor, Flynn, Mooney, Penman
Livingston: George, Brandon, Obileye, Nottingham, Sangare, Carson, Kelly (Mackay 83), Holt, Shinnie (Devlin 66), Nouble, Yengi (Guthrie 88)
Subs Not Used: McGovern, Anderson, Kelly, Ledingham, Culbert, Lawal
Referee: Euan Anderson
Assistant Referee: Frank Connor
Assistant Referee: John Stewart
Fourth Official: Dan McFarlane
VAR: Kevin Clancy
