After a close encounter in the quarter-final of the men's -66kg category between Japan's Ebinuma Masashi and South Korea's Cho Jun-Ho, the referee and judges on the mat raised their blue flags to indicate Cho had won.
Cho began punching the air in delight, but the arena at London's ExCel Centre erupted in derision with the disgusted Japanese coach looking utterly flabbergasted. The result was referred to a reviewing commission and they ruled that Masashi should be the winner.
Nicolas Messner, spokesman for governing body the International Judo Federation, said it was the first time the referee and judges had been overruled on a flag decision.
"We want to make sure that the right fighter has won," he said. "The fight was very close."
Ebinuma went on to lose his semi-final, but beat Poland's Pawel Zagrodnik to earn a bronze medal.
And while Cho lost out on a chance of gold, he did at least come through the repechage and also won a bronze medal against Spain's Sugoi Uriarte.
Before the tournament began, the IJF said it was keen to avoid the furore over decisions in the past such as the 2000 Olympic heavyweight final in Sydney.
That clash saw French judoka David Douillet take gold from Japan's Shinichi Shinohara amid angry protests from the Japanese camp.