bug reporting - Where to report mistakes in a translated man page?

I just discovered a mistake in the German version of the man page for adduser:

Einen System-Benutzer einrichten
Wird adduser ohne die Option --system und mit einem nicht optionalen Argument aufgerufen, richtet adduser einen System-Benutzer ein.

However, in the English version which I'm reading at http://manpages.ubuntu.com/manpages/xenial/en/man8/adduser.8.html we have

Add a system user
If called with one non-option argument and the --system option, adduser will add a system user.

The mistake is the word ohne (without), which should be replaced by mit (with). This actually confused me for quite some time, so I think it should really be corrected. But where can I report this "bug"? I read here that man page errors are bugs, but the error is only in the translated version.

Edit: Thanks to muclux's answer I have filed a bug report against the project Ubuntu Translations:

https://bugs.launchpad.net/ubuntu-translations/+bug/1743251

See Reporting Bugs - there is a section on translation errors.