Polonia Warsaw attempted to demonstrate a bit of fair play in their match against Blekitni Gabin in the lower echelons of Polish football, and it backfired spectacularly.
After a break in play for an injury, Polonia decided to restart the game by knocking the ball back to the opposition goalkeeper from the halfway line.
Dominik Lemanek, however, didn't notice the goalkeeper was out of position when he took the kick—and the ball went straight into the back of the net, making it 2-0 to Warsaw.
With the goal coming in the final minute of the match, there was no time to make up for it. As a result, the goal stood (as recorded by Gabin's website in Polish), and Polonia won by an extra goal.
[YouTube, h/t Reddit]