Cannot select desktop Background in KOI-8

[AsstZD]

When clicking the Backgrounds applet in the Settings, nothing happens. In Terminal, the Python exception is visible:

 ...cs_backgounds.py, line 130, in on_module_selected
 path = subprocess.check_output(["xdg-user-dir", "PICTURES"]).decode("utf-8").rstrip("\n")
 UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe9 in position 13: invalid start byte

This is apparently caused by my locale, being "ru_RU.koi8-r". When I set the locale to C, it opens, but all the folders are empty. The terminal is spammed with:

 Failed to convert /usr/share/backgrouns/blah.jpeg: UnicodeDecodeError: 'utf-8' codec can't decode byte.....

etc.