Philippe Gilbert's record on the Côte de la Redoute stood for barely 24 hours before it was toppled by Jumbo-Visma Development Team rider Gijs Leemreize.
Gilbert had been challenged by his brother with taking the Strava KOM on the iconic climb that is often decisive in Liège-Bastogne-Liège, which he won in 2011.
The former world champion completed the 1.6km ascent, which has an average gradient of 9.5 per cent, in a time of 4:25, knocking some 17 seconds of the previous benchmark held by Romain Bardet.
Posting on social media on Friday morning, Gilbert challenged others to get involved, saying: "Try to beat it!"
Leemreize, a 20-year-old Dutch rider, did just that, tackling La Redoute half-way through a 106km ride later on Friday. He took three seconds off Gilbert's time, clocking 4:22 after riding up at an average speed of 21.2km/h.
"Hey, Philippe Gilbert, that KOM of yours was short lived," the Jumbo-Visma Development Team posted on social media.
"Hahaha, class, little one," wrote Jumbo-Visma's Robert Gesink.
Leemreize is a third-year U23 rider who describes himself as a climber. Last year he won the Topcompetitie uphill time trial, and this year he had his first taste of pro racing as he was called up the the Jumbo-Visma elite squad for the Tour de la Provence, where he placed 33rd overall.
