Tom Craddock struck twice as Oxford ended league leaders Port Vale's fantastic run of form with a 2-1 win.
And the striker's winner came in dramatic fashion in stoppage time, just a minute after Gareth Owen had snatched an equaliser that had looked like bringing Micky Adams' men a point.
The Valiants were bidding for a seventh successive win but they were stopped in their tracks first by Craddock's 61st-minute header in a thrilling encounter at the Kassam Stadium.
Running in from deep the former Luton striker planted an eight-yard header past Stuart Tomlinson and into the far corner of the goal.
However, as the game entered injury time, centre back Owen popped up in the area to drive in a leveller from 15 yards.
But Vale's joy at that goal almost immediately turned to disappointment as substitute Matt Green touched a pass to his left and Craddock coolly slotted home his second - and the winner.