Saints kept their hopes of snatching the final European spot alive with a hard-fought win over Aberdeen in Paisley.
The only goal came on the hour mark, Mikael Mandron celebrating his new contract by controlling Mark O'Hara's free-kick on his chest before volleying past Dimitar Mitov.
The Dons had had Jeppe Okkels' first-half goal ruled out for handball and rarely threatened to draw level, in the end only some great saves from Mitov in stoppage time stopping Saints extending their winning margin.
There was one change to the Saints side which drew with Rangers, Oisin Smyth getting the nod in midfield over Caolan Boyd-Munce who dropped to the bench. Kevin Nisbet led the attack for the Dons with former Buddie Jamie McGrath having to make do with a place on the bench.
The visitors enjoyed plenty of early pressure, forcing a series of corners before Leighton Clarkson shot into the side netting. Saints threatened for the first time when a short corner routine forced Dimitar Mitov to palm away Oisin Smyth's delivery. Midway through the half a great cross from the right was volleyed home by Okkels to put Aberdeen in front, however the Saints players were adamant Nisbet had handled in the build-up. After a lengthy delay, referee Ross Hardie was eventually called to look at the monitor and decided to rule it out – much to the delight of the Paisley faithful.
That decision seemed to spur Saints on, a tremendous pass from Smyth finding Jonah Ayunga and he cut in before firing narrowly wide from 20 yards. Good work from Ryan Alebiosu then saw his cross knocked as far as Mark O'Hara, whose low shot was held by Mitov at the second attempt. The game had come to life following VAR's intervention, Shayden Morris' shot being deflected just wide before Mitov got down to save an effort from Mandron. A lovely touch from the Frenchman then gave him a sight of goal from the edge of the box but it was on his weaker foot and his shot trundled wide.
Mandron's attempted overhead kick earned him a somewhat harsh booking just after the break before Topi Keskinen dragged a shot wide for the visitors. As the hour mark approached Saints took the lead, O'Hara flighting a free-kick into the box that Mandron took on his chest before thumping a volley past Mitov. Once again there was a pause for a VAR check, this time for offside, but on this occasion the goal stood.
Zach Hemming had had a fairly quiet afternoon but needed to be alert to turn away a cross from sub McGrath that threatened to sail into the top corner. The keeper was then involved in a nasty looking clash with Nisbet that left both players needing treatment but thankfully both were able to continue.
Another sub, James Scott, had the chance to seal things in stoppage time from Mandron's cut-back but he shot straight at Mitov, although the flag then went up for an earlier offside. Great work from Roland Idowu on the break gave Scott another chance, this time it was blocked with VAR deciding there hadn't been a handball. Still Saints refused to settle for one goal, Idowu drawing a great save from Mitov in the final few seconds as the Buddies celebrated a first ever top six win at home.
Full-Time: St Mirren 1-0 Aberdeen
St Mirren: Hemming, Fraser, Gogic, Taylor, Alebiosu, Phillips, Smyth (Boyd-Munce 67), O'Hara (c) (Scott 79), John, Mandron, Ayunga (Idowu 46)
Subs Not Used: Urminsky, Tanser, McMenamin, Kiltie, Oseni
Aberdeen: Mitov, Devlin, Dorrington (Gueye 83), Knoester, Shinnie (c), Clarkson (McGrath 55), Palaversa (Boyd 83), Okkels (Polvara 55), Morris, Keskinen (Dabbagh 66), Nisbet
Subs Not Used: Doohan, Mackenzie, Milne, Ambrose
Referee: Ross Hardie
Assistant Referee: Alastair Taylor
Assistant Referee: Ross Nelson
Fourth Official: Euan Anderson
VAR: Steven McLean
Attendance: 7,587