Third Division leaders East Fife dumped top-flight St Mirren out of the CIS Insurance Cup thanks to a wonderful Craig O'Reilly goal.
Craig O'Reilly scored a spectacular winner
East Fife striker Steven Nicholas sent a drive against the post before Saints striker Alex Burke had an effort chopped off for offside.
Nicholas squandered a chance while Willie McCulloch saved well from Burke.
But O'Reilly settled the game after 63 minutes, unleashing an unstoppable shot that went in off the crossbar.
St Mirren had survived that scare from Nicholas' effort from the edge of the box.
But that was the only real action from the opening spell as the lower league side did enough to keep Gus MacPherson's men at bay.
Nicholas wasted a glorious chance from just a few yards out for the Methil outfit after being picked out inside the box, poking his shot harmlessly wide of goalkeeper Chris Smith.
Burke warmed the hand of East Fife keeper McCulloch with a long-range shot, but that was all the home side could muster before the break.
Saints defender Will Haining almost handed O'Reilly an opportunity after 55 minutes.
His pass-back fell short and within range of the Fifers' half-time substitute, but keeper Smith raced smartly from his line to clear the danger.
But O'Reilly came up trumps with a strike that stunned the majority of the 1,782 Paisley crowd.
The bustling striker looked to be running out of ideas as he cut in from the right.
But he unleashed a drive that crashed off the underside of the bar before landing behind Smith.
Dave Baikie's side were on the retreat from then on, but their aerial strength was proving key to keeping the Buddies at bay.
Saints introduced Alan Reid and Stephen O'Donnell to the play, but the home side struggled to create any clear-cut chances against the resistance of the visitors.
O'Reilly even had an opportunity at the death to add more misery to the home side.
But his effort when faced with only the keeper was disappointing and straight at Smith.
St Mirren: Smith, van Zanten, Mason (O'Donnell 79), Haining, Potter, Murray, Brittain (Reid 67), Burke (Kean 61), Corcoran, Mehmet, Miranda.
Subs Not Used: Howard, Brady.
East Fife: McCulloch, McDonald, Smart, Tweed, Fotheringham, Blackadder, Walker (O'Reilly 46), Stewart, Cameron, Nicholas (Martin 49), Gordon.
Subs Not Used: Fox, Linton, Young.
Goals: O'Reilly 63.
Ref: S Conroy