Image scaling doesn't work?

Hi !

I try to make the “image scaler” work… but it doesn’t (or I didn’t understand how to do it)
From what I understand, images that are smaller than [image_scaler_max_filesize] can be reduced by adding “?width=XXX” at the end of the URL (where XXX = desired size)
In issues, inserted imaged are displayed in their original size, no matter the value I put at the end of the URL and no matter the weight of my image.

Image: 512x512 (PNG 462Ko or PNG 185Ko or JPG 23Ko)

Result: image 512x512

In gitlab.rb I added
gitlab_workhorse[‘image_scaler_max_procs’] = 10
gitlab_workhorse[‘image_scaler_max_filesize’] = 256 * 1024

What I missed?

Personal GitLab instance v13.9
On Ubuntu server 18.04.5