Shaun Maloney rifled home a controversial late winner to break Motherwell hearts as Celtic won 2-1 to go into the CIS Insurance Cup final.
The usually reliable Artur Boruc's calamitous mistake in the 12th minute gifted Motherwell a shock lead.
Boruc, the Polish number one, made a complete mess of a cross to allow Richie Foran to head the Steelmen into a surprise lead.
Maciej Zurawski had saved the blushes of club and country team-mate Boruc with a first-half equaliser.
Maloney flicked a fine reverse pass into the path of the Pole, who managed to force the ball into the net, despite the goalkeeper getting a foot to it.
And livewire Maloney had the final say by blasting John Hartson's indirect free-kick through a ruck of Motherwell players and into the net, after referee Craig Thomson had adjudged Graeme Smith to have collected Martyn Corrigan's poor back-pass.