Comment 63 for bug 1267059

> have you made sure you manually set that option to 'true'? It's 'false' by default.

yes,

root@mailhost:~# grep Dependencies /etc/apt/apt.conf.d/50unattended-upgrades
Unattended-Upgrade::Remove-Unused-Dependencies "true";

root@mailhost:~# ls -lht /etc/apt/apt.conf.d/50unattended-upgrades
-rw-r--r-- 1 root root 2.1K May 8 2013 /etc/apt/apt.conf.d/50unattended-upgrades