Tray icon size is 24x24 when set to 22x22

I have the Status Tray Plugin set to fixed icon size 22 pixels. I noticed that the displayed icon isn't the icon themes' 22x22 icon, but instead the 24x24 icon cropped to 22x22.

I then edited my icon theme to make sure if the 24 icon was used, by writing over the icons. Indeed that was the case.

This issue also appears on all other xfce4 apps like xfce4-terminal, parole, gigolo, xfmpc. Not an issue with blueman or networkmanager icons, therefore not a panel tray issue.

Tested on latest master.