Second Division part-timers Stenhousemuir produced a major shock as they knocked out Scottish Communities League Cup holders Kilmarnock.
Brown Ferguson fired Stenny ahead after 19 minutes when Ryan O'Leary fouled John Gemmell following a cross into the box from Greg Ross.
It was Gemmell who headed the Scottish Premier League side further behind two minutes before the break.
Killie pressed forward after the break and Michael Nelson added a late reply.
But Stenhousemuir held on during four frantic minutes of stoppage time and are still unbeaten in all competitions this season.
Ferguson celebrates after putting Stenhousemuir ahead at Rugby Park
Kilmarnock had five of their League Cup-winning team missing through injury, but manager Kenny Shiels paid Stenny plenty of respect by makinge only one change from the side that defeated Dundee United on Saturday, with Lee Johnston replacing Liam Kelly in midfield.
Former Killie defender Martyn Corrigan made two changes to the Stenny side from the weekend draw away to Stranraer, with Ferguson and Kevin McKinlay coming in for Andy Rodgers and Craig Anderson.
And it was the experienced Ferguson who put the visitors ahead as their counter-attacking formation proved dangerous from the kick-off.
The towering Gemmell provided a huge target up front and, after O'Leary held the striker's shirt, Ferguson stepped up to calmly send goalkeeper Kyle Letheren the wrong way.
Gemmell sent a speculative 30-yard half-volley over the crossbar and Bryan Hodge's left-foot shot minutes later was deflected inches wide off Michael Nelson as Stenny threatened to extend their lead.
Kilmarnock's Jude Winchester missed an open goal from six yards after Danny Racchi drilled the ball across the face of goal.
The holders paid for that miss five minutes later when Ferguson's deep corner-kick was misjudged by Letheren and the ball was headed into the empty net by Gemmell.
Shiels introduced tricky winger James Dayton at the interval and the Englishman was involved in a move that led to Rory McKenzie having his low shot held by Callum Reidford.
Racchi then sliced a volley a few inches too high from the edge of the 18-yard-box and McKenzie'sright-foot effort from 25 yards rattled the goalkeeper's left-hand post.
Stenny were camped inside their own half for long spells in the last 20 minutes and substitute William Gros rifled another 30-yard effort into the palms of Reidford.
Substitute Darren Smith curled a 25-yard shot past Kilmarnock's far post before Nelson headed home a Dayton free-kick with the game heading into injury-time.
Killie came within inches of taking the game to extra-time as the injured Reidford clutched the ball amid an almighty scramble just yards from goal seconds before the final whistle.
: "If you look at what happened on Saturday when we were fantastic against Dundee United, we didn't get much credit and it was all about how poor they were, so I don't want to come across that way and talk about how poor we were.
"I'd rather give credit to Stenhousemuir than talk about some of the faults in our play.
"They came here and played really well, were 2-0 up at half-time and it should have been more, and they were better than us and we're disappointed with the outcome."
Stenhousemuir manager Martyn Corrigan
: "That was good. It was delightful.
"We set our stall out, but ideally we want to play football in the right manner and we played some attacking stuff at times and, credit to the players, they worked tremendously hard and they got their rewards in the end.
"We didn't sit in. We played an attacking formation and you can see the boys were enjoying the game.
"We've got a right good team this season. They are comfortable on the ball.
"I think what you're seeing is that the lower divisions are getting closer to the SPL and that's something the country has not had for a wee while."
Full Time The referee signals the end of the game.
Darren Smith sends in a cross. Danny Racchi challenges Bryan Hodge unfairly and gives away a free kick. Direct free kick taken by Stewart Kean.
A cross is delivered by Jude Winchester, Scott Buist manages to make a clearance.
Michael Nelson takes a shot. Save made by Callum Reidford.
Assist by James Dayton.
89:23 Goal scored
Goal! - Michael Nelson - Kilmarnock 1 - 2 Stenh'muir Michael Nelson finds the net with a headed goal from close in. Kilmarnock 1-2 Stenhousemuir.
Substitution Andy Rodgers replaces Sean Dickson.
Unfair challenge on James Dayton by Scott Buist results in a free kick.
Centre by Danny Racchi, clearance by Bryan Hodge.
Darren Smith has an effort at goal from just outside the box which goes wide of the right-hand post.
The ball is sent over by Danny Racchi. Outswinging corner taken right-footed by Danny Racchi from the right by-line to the near post, clearance by John Gemmell.
James Dayton crosses the ball.
Effort from 30 yards by William Gros. Save by Callum Reidford. The ball is delivered by Michael Nelson, save made by Callum Reidford.
Foul by Rory McKenzie on Kevin McKinlay, free kick awarded. Direct free kick taken by Callum Reidford.
Substitution Darren Smith on for Brown Ferguson.
The ball is sent over by James Dayton, Kevin McKinlay manages to make a clearance.
The ball is sent over by James Dayton, clearance made by Kevin McKinlay.
Danny Racchi produces a cross, clearance made by Ross McMillan. Corner taken by Danny Racchi. Manuel Pascali has an effort at goal from deep inside the area missing to the right of the goal.
Centre by Mark O'Hara, Close range shot by Ryan O'Leary goes wide of the right-hand upright.
James Dayton produces a cross, Greg Ross gets a block in. Outswinging corner taken by James Dayton, Scott Buist makes a clearance.
Effort on goal by James Dayton from just inside the area clears the crossbar.
Centre by Danny Racchi, Bryan Hodge makes a clearance.
Free kick taken by James Fowler. James Dayton produces a right-footed shot from outside the penalty box and hits the bar.
Booking The referee cautions Greg Ross for unsporting behaviour.
Free kick awarded for a foul by Greg Ross on James Dayton.
John Gemmell takes a shot. Blocked by Ryan O'Leary.
Kevin McKinlay takes the direct free kick.
Booking Mark O'Hara is given a yellow card.
Mark O'Hara gives away a free kick for an unfair challenge on Sean Dickson.
Substitution Craig Anderson replaces Iain Thomson.
John Gemmell is flagged offside by the assistant referee. Kyle Letheren takes the indirect free kick.
Effort on goal by Iain Thomson from outside the box goes harmlessly over the bar.
James Fowler sends in a cross.
Booking Iain Thomson goes into the book for unsporting behaviour.
John Gemmell is flagged offside by the assistant referee. Indirect free kick taken by Kyle Letheren.
John Gemmell is flagged offside by the assistant referee. Indirect free kick taken by Manuel Pascali.
Brown Ferguson has an effort at goal from outside the box which misses left.
Inswinging corner taken by Brown Ferguson.
Danny Racchi produces a right-footed shot from just outside the penalty area that goes harmlessly over the target.
Shot by Michael Nelson from 35 yards. Save by Callum Reidford.
The ball is crossed by James Dayton. A cross is delivered by Ryan O'Leary, Greg Ross makes a clearance.
Stewart Kean produces a cross, Ryan O'Leary manages to make a clearance.
Booking The referee shows Stewart Kean a yellow card for unsporting behaviour.
Unfair challenge on Michael Nelson by Stewart Kean results in a free kick. Direct free kick taken by Kyle Letheren.
Kyle Letheren takes the free kick.
Substitution Borja Perez leaves the field to be replaced by William Gros.
The assistant referee flags for offside against Stewart Kean.
Iain Thomson gives away a free kick for an unfair challenge on Jude Winchester. Jude Winchester takes the free kick.
The ball is swung over by Rory McKenzie, Ross McMillan gets a block in.
Greg Ross concedes a free kick for a foul on James Dayton. James Fowler restarts play with the free kick.
Sean Dickson sends in a cross.
Danny Racchi crosses the ball in from the free kick, save made by Callum Reidford.
Booking Booking for Scott Buist for unsporting behaviour.
Free kick awarded for an unfair challenge on James Dayton by Scott Buist.
Brown Ferguson takes the inswinging corner, John Gemmell gives away a free kick for an unfair challenge on Michael Nelson. Kyle Letheren takes the direct free kick.
John Gemmell gives away a free kick for an unfair challenge on Mark O'Hara. Mark O'Hara restarts play with the free kick.
A cross is delivered by Stewart Kean.
A cross is delivered by Jude Winchester, blocked by Kevin McKinlay. Corner taken by James Dayton from the right by-line played to the near post, Scott Buist manages to make a clearance.
James Dayton delivers the ball, Brown Ferguson makes a clearance. Corner taken right-footed by Danny Racchi from the left by-line, Greg Ross manages to make a clearance.
Shot from 20 yards from Rory McKenzie. Save made by Callum Reidford.
The referee starts the second half.
Substitution Lee Johnson leaves the field to be replaced by James Dayton.
45:00 +1:03 Half time
Half Time The referee blows for half time.
Iain Thomson concedes a free kick for a foul on Rory McKenzie. Danny Racchi fires a strike on goal direct from the free kick.
The assist for the goal came from Brown Ferguson.
42:54 Goal scored
Goal! - John Gemmell - Kilmarnock 0 - 2 Stenh'muir John Gemmell finds the back of the net with a headed goal from inside the six-yard box. Kilmarnock 0-2 Stenhousemuir.
Kevin McKinlay crosses the ball, Mark O'Hara gets a block in. Corner taken right-footed by Brown Ferguson,
The ball is delivered by Greg Ross, Mark O'Hara manages to make a clearance. The ball is delivered by Greg Ross, James Fowler gets a block in. Bryan Hodge takes a inswinging corner.
Centre by Sean Dickson, Mark O'Hara manages to make a clearance.
Free kick awarded for an unfair challenge on Jude Winchester by Greg Ross. Direct free kick taken by Lee Johnson.
The ball is sent over by Danny Racchi, Shot by Jude Winchester from inside the six-yard box clear the bar.
Lee Johnson sends in a cross.
Centre by Lee Johnson, Scott Buist makes a clearance.
The ball is delivered by Greg Ross, save made by Kyle Letheren.
Shot from outside the area by John Gemmell misses to the left of the target.
Iain Thomson gives away a free kick for an unfair challenge on Manuel Pascali. Lee Johnson takes the direct free kick.
Booking Bryan Hodge is shown a yellow card for unsporting behaviour.
James Fowler crosses the ball, save by Callum Reidford.
Michael Nelson takes a shot. Blocked by Michael Nelson. Corner taken right-footed by Brown Ferguson to the near post, Header from close range by John Gemmell clears the bar.
Lee Johnson concedes a free kick for a foul on Brown Ferguson. Bryan Hodge takes the free kick.
Unfair challenge on Mark O'Hara by John Gemmell results in a free kick. Direct free kick taken by Kyle Letheren.
Iain Thomson gives away a free kick for an unfair challenge on Borja Perez. Lee Johnson takes the direct free kick. The referee blows for offside. Callum Reidford restarts play with the free kick. Long range shot by John Gemmell goes over the bar. Borja Perez gives away a free kick for an unfair challenge on Scott Buist. Scott Buist takes the free kick.
James Fowler takes a shot. Save by Callum Reidford.
Assist on the goal came from John Gemmell.
19:56 Goal scored
Goal! - Brown Ferguson - Kilmarnock 0 - 1 Stenh'muir Power penalty scored by Brown Ferguson. Kilmarnock 0-1 Stenhousemuir.
Booking Caution for Ryan O'Leary.
Centre by Greg Ross, Ryan O'Leary challenges John Gemmell unfairly and gives away a Penalty.
Substitution Jeroen Tesselaar leaves the field to be replaced by Mark O'Hara.
Danny Racchi delivers the ball.
Rory McKenzie takes a shot. Greg Ross gets a block in.
Free kick awarded for a foul by Scott Buist on Rory McKenzie. Danny Racchi delivers the ball from the free kick right-footed from left wing, John Gemmell manages to make a clearance.
Free kick awarded for a foul by Iain Thomson on Borja Perez. Free kick taken by Manuel Pascali.
The ball is delivered by James Fowler, Ross McMillan manages to make a clearance. Short corner worked by Danny Racchi.
Free kick awarded for an unfair challenge on Brown Ferguson by Jude Winchester. Free kick taken by Bryan Hodge.
Effort on goal by Iain Thomson from outside the area goes harmlessly over the bar.
Iain Thomson gives away a free kick for an unfair challenge on Borja Perez. Michael Nelson takes the free kick.
Unfair challenge on Brown Ferguson by Jeroen Tesselaar results in a free kick. Free kick taken by Callum Reidford.
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