How can I force Firefox to change all icons?

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http://askubuntu.com – I installed the faenza-icon-set via ppa, and it works fine - except in firefox: Some icons are replaced by faenza (forward, back, home, copy, cut ...) and some icons not (favorites, history, downloads, new window, new tab ...). How can I force Firefox to replace all icons by the new theme? The GTK+ Native Theme doesn't help. It only changed something with the tabs ... (HowTos)