How to prevent schroot from overridding passwd file and others files already present on the chrooted system?

When I had to repair my Debian system, I tried to use schroot due the convenience of not having to mount bind several partitions. But, contrary to my expectations, schroot decided to override my passwd file and other configuration files (in /etc and my home directory) which I didn't like (and sometimes causes [weird messages](https://unix.stackexchange.com/questions/160486/error-message-unknown-user-geoclue-in-statoverride-file)) . Is there a way to prevent that behavior? I used the type directory for schroot, since it seemed the one I needed. I checked the man page and only found a --preserve-environment option, but from its description I'm not sure if it preserves the chrooted system environment or just copies my user environment to the chroot session instead of a clean slate (which is the default).