Refresh favicon in bookmarks (Firefox)

Few days ago, I've changed the favicon of my website: it works well when I open the website:

My website is also in my bookmarks, but it shows the old favicon:

I already had a look here, but answers did not solved my problem. The solution is probably very simple, but I have not found anything so far.

Thanks!

There is a solution that works on every browser:

• go to www.yourwebsiteurl.com/favicon.ico (works for localhost as well)

• force refresh (Ctrl+F5 for most browsers, or manually)

• restart the browser