appindicator doesn't honor the color key in -symbolic icons

I'm creating an app that uses libappindicator to add an status icon to the bar. I want to ensure that the icon remain visible no matter what background color is being used in the upper bar, so I followed the "-symbolic" standard from freedesktop. It specifies that icons whose name ends with "-symbolic" will have fills with #BEBEBE color replaced by the current FG-COLOR, allowing them to be visible both with dark and light backgrounds.

I did it and it worked fine under Gnome-Shell, but not with unity (I tested both my current 12.04 system and a 12.10 in a virtual machine). I made several tests, both with my own icons and other system icons which are "-symbolic", but no results.

Several notes about symbolic icons:

http://www.freedesktop.org/wiki/SymbolicIcons
http://git.gnome.org/browse/gnome-icon-theme-symbolic/tree/README
http://askubuntu.com/questions/148955/why-do-the-gnome-symbolic-icons-appear-darker-in-a-running-application

Thanks.