In the frame, the actor can be seen sporting his signature green and black Slytherin cloak.
"Agings a b----," he captioned the picture.
As soon as the star shared the picture on the photo-sharing application, his fellow former co-star, Matthew Lewis, who played the role of Neville Longbottom in the highly-appreciated series, had something else to say about ageing.
"Speak for yourself lad," the 30-year-old star wrote back.
According to E! News, the two have stayed close friends since the final 'Harry Potter' film wrapped nearly a decade ago and have even had several meet-ups over the years.
In August 2018, the two reunited with former co-star Emma Watson, who played Hermione Granger in the franchise.