VAR threatened to deny St Mirren a deserved victory before super sub Alex Greive grabbed his side another clinical late winner.
The dominant Buddies hit the woodwork three times against Dundee United with Charles Dunne, Curtis Main and Jonah Ayunga all inches away from netting.
Main gave the hosts a first half lead with a close-range header before the Terrors equalised early in the second as substitute Steven Fletcher fired the visitors level.
