Canon EF 20mm Clicking Aperture

Scenes

Filmmaker
Jun 12, 2014
142
131
UK
Just picked up a Canon EF 20mm f2.8 second hand nearly mint condition in box for my R6 and loving it so far but it clicks when I adjust the aperture. I’ve had a fair few EFS, EF RF lenses and never noticed any do that before.

It seems to work and It is a 30yr old lens design. Just wondered if anyone else has experience with a copy and if it was normal? Thanks in advance.