What was meant to be a celebratory high-five between Mr Corbyn and the UK's Shadow Foreign Secretary Emily Thornberry quickly turned into a very awkward, and very public, gaffe.
First, the jubilant Mr Corbyn and Ms Thornberry hugged for a photo-op. Then, they excitedly pointed at each other. And then, Mr Corbyn went in for a high-five. That's when this happened:
Worst high 5 of all time...? pic.twitter.com/XyIE5oYt7H— Dan Hewitt (@danhewittsky) June 9, 2017
"Worst high 5 of all time...?" asked Dan Hewitt, who posted the clip to Twitter.
It's too painful to watch! *watches 57 more times*— Chi Rising (@chisherman) June 9, 2017
Horrifyingly awkward in the most endearing of ways!— SaveTheKeys (@SheTypesAlot) June 9, 2017
Usually both parties are to blame in a botched high-five, but this one's all Corbyn. There was never a high-five on the table. Never in play https://t.co/xKbrtoTa0H— Jon Healy (@JonHealy) June 9, 2017