Benjamin Siegrist made a rare blunder as Dundee United crashed out of the Scottish Cup to Celtic.
Swiss keeper Siegrist spilled a Daizen Maeda cross into the path of Georgios Giakoumakis to hand Celtic their second goal.
United had fallen behind to an early Callum McGregor effort.
But they went toe-to-toe with Celtic for long spells without finding a route to goal before Benji’s blunder.
And Giakoumakis grabbed his second late on to clinch the win for Celtic.
Dundee United hadn’t beaten Celtic in the Scottish Cup since 1981.
Back then a Paul Hegarty double and Eamonn Bannon strike was enough to helped United claim a 3-2 semi-final replay win.
They were seeking their first win over Celts in any competition since 2014 but were in bouyant mood before the game.
The club responded to calls from their fans to open up The Shed to home supporters.
And the supporters responded by creating a real cup tie atmosphere with displays at both ends of the pitch.
The noise levels were cranked up to the maximum at kick-off and the stage was set for a cracking cup tie.
United were dealt a blow in the build-up with Tony Watt ruled out through injury.
They recalled Dylan Levitt to the midfield and skipper Ryan Edwards recovered from a broken nose to marshall the defence.
Dundee United lose early Celtic goal
But they found themselves a goal down inside 12 minutes.
Matt O’Riley’s short corner found James Forrest and he set up McGregor to drill the ball home through a ruck of bodies from 18 yards.
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It was exactly the start United DIDN’T want.
With Celtic ahead, they were able to settle and play their trademark passing game.
McGregor looked particularly impressive in midfield for Celtic.
And United were dealt a further blow in 28 minutes as they lost Ian Harkes through injury, with Kevin McDonald replacing him.
The hosts then felt aggrieved as Hatate wiped out Kieran Freeman on the touchline.
Home fans called for a red card but referee John Beaton elected instead to show yellow.
To their credit, United refused to allow Celtic to run away with it.
Celtic had the ball in the net again via Daizen Maeda but it was ruled out for a handball by Giakoumakis.
McDonald was a steadying influence in midfield and they were still very much in this game going into the break.
But they needed more threat going forward with an off-target long-range Edwards strike their only chance in the first period.
United emerged from the break looking pumped up.
With The Shed in full voice, they started to get in the faces of the Celtic defence.
Ilmari Niskanen and Freeman were pushed further forward and Celtic looked nervy at the back.
But again, United didn’t create enough.
And they were punished in the cruellest of fashions.
Siegrist has been outstanding for United, time and time again over the last few years.
But for once he wasn’t their saviour as he fumbled a Maeda cross straight to Giakoumakis to prod home from two yards.
United then handed a debut teenager Miller Thomson who became the 15th academy graduate to star for the first team this year.
Thomson looked lively but watched on as Giakoumakis squeezed home a Karamoko Dembele cross for the third.
Teams for Dundee United v Celtic
Dundee United: Siegrist; Smith, Freeman (Sporle, Graham, Edwards, Butcher, Levitt (Meekison 73), Niskanen, Harkes (McDonald 28), McNulty (Thomson 73), Clark. Subs: Eriksson; Mulgrew, Akinola, Neilson, Cudjoe-Anim.
Celtic: Hart; Taylor, Starfelt, Carter-Vickers, Juranovic, McGregor (Ideguchi 88), O’Riley (Johnston 76), Hatate (Rogic 46), Maeda (Dembele 76), Giakoumakas, Forrest. Subs: Bain; Jullien, Bitton, Ajetic, McCarthy, Ralston, Welsh.
Referee – John Beaton