A 100-strong bunch of riders were hurtling along the Belgian tarmac with 60 kilometres remaining when a colourful arch in the distance started bobbing dangerously.
A man stepped in to hoist it into the sky with his hand as the cyclists flew past, and two people on the grass verges also pushed desperately to raise it, with everyone somehow managing to sneak through unscathed.
A camera on the back of a motorcycle revealed how close the race had come to mass chaos, with the lower portion of the arch practically brushing some cycle helmets.
It was another unwelcome episode from an incident-packed race that saw two crashes involving service cars.
Norway's Alexander Kristoff outsprinted Niki Terpstra to win the gruelling 264km cobbled classic.