It turns out that the current stable Debian (stretch) suffers from this bug, too. Luckily, it's easy to recompile the "quota" package and patch it:
# follow this tutorial: https://wiki.debian.org/BuildingTutorial#Rebuild_without_changes
apt-get source quota
apt-get build-dep quota
apt-get install devscripts
# this package uses "quilt" for ...