Paul Mullin scored with seconds remaining as Cambridge beat Walsall 1-0.
Injury time was up when League Two's top scorer unleashed a superb effort into the top corner from outside the box.
It was Mullin's 23rd league goal of the campaign, moving him to within one of equalling the club's record for EFL goals in a season.
Before then it was the visitors who were more likely to find a winner. After 21 minutes they appealed for a penalty as Kyle Knoyle brought down Max Melbourne, but referee Ben Toner awarded a free-kick just outside the box.
Moments later Us keeper Callum Burton did well to tip over Emmanuel Osadebe's acrobatic volley after Cameron Norman's long throw fell to him.
The visitors had two other openings before half-time, but Hayden White and sub Tyreik Wright both fired off target from dangerous positions.
Eighteen minutes from time Osadebe's cross from the by-line was diverted wide by Josh Gordon, leaving the game poised to end goalless before Mullin's terrific winner at the death.