Colney Heath came within a minute of claiming a deserved point at unbeaten Shefford Town & Campton before being stung again.
The home side had won all three games in the Spartan South Midlands League Premier Division prior to the Magpies' visitors but the game was head to a 0-0 draw as the match entered stoppage time.
But with time almost up, a long throw into the box from Dan Hammer saw the ball fall for James Younger and the substitute poked the ball over the line to give Shefford the 1-0 win and send them top of the pile.
It was tough on Heath who had more than played their part and could have taken all three points themselves.
It was also the second league game in a row that was decided by a solitary goal in stoppage time, with both occasions going against the Magpies.
Both teams had a lot of possession during the first half at Shefford Sports Club but it was Colney who had the better of the chances.
George Sippetts was deceived by a bobble off the hard ground and screwed his shot wide while an Ollie Regan effort was saved by home goalkeeper Kyle Forester.
Forster also denied a Hadley Gleeson header after a great cross by Dominic Knaggs before getting down low to stop a Yasin Boodhoo shot.
Connor Sansom played his part too in the Magpies' goal, saving an Ash Ingham header.
The home side also chances after the break, Charlie Thake putting one over the top, but Colney continued to create as well.
Deondre Pascoe and Tejon Brown went close while the dangerous Kwon Hepburn flashed a wonderful ball across the six-yard box but just too far in front of the strikers.
For all that, it did look as if they were set for a good point and to break Shefford's perfect start until the final moments.
Colney Heath play another unbeaten side, Crawley Green, at home on Saturday.
London Colney's FA Vase hopes ended in the first qualifying round with a 4-1 loss away to Harefield United.
Bobby Webb got their only goal.
Harpenden Town meanwhile had a bye and make their bow in the next round with a home tie against SSML Division One side, Northampton ON Chenecks.
Harps are at home in the league on Saturday with the Blueboys of London Colney the visitors.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here