No icons appear in urxvt

I'm trying to set up colorls on my linux-machine, and so far the application is working, but I lack the knowledge on how to get the icons to appear in my urxvt window.

Here's the font-line from my .Xresources:
URxvt*font: xft:DroidSansMonoForPowerline Nerd Font:pixelsize=15:antialias=true:hinting=true:autohint=true
This line works fine, it uses the proper typeface, but sadly the icons all appear as boxes.

Have I missed something, or is urxvt simply not capable of showing the icons?

Start by reproducing colorls in urxvt using the .Xresources font line shown in the report, then check whether the terminal can render the icon glyphs rather than boxes. Confirm the result with the reported setup and document the required configuration or the limitation so icons display correctly.

Written by the indexing model from the issue text.