Comment 11 for bug 839775

For people looking for a good workaround:

I've installed faenza-icon-theme from ppa:tiheum/equinox
It's great theme, so you could just change to it (with help of gnome-tweak-tool), and probably be happy.
But I still prefer ubuntu-mono, so I did this trick:
Copy /usr/share/icons/ubuntu-mono-dark to ~/.local/share/icons/ubuntu-mono-dark
Edit index.theme: replace Inherits=Humanity-Dark,gnome,hicolor with Inherits=Faenza-Ambiance,Humanity-Dark,gnome,hicolor
Regenerate cache: gtk-update-icon-cache .
Now I have missing search icon from faenza theme, it fits very nice. Don't know about other icons.