[plt-scheme] Getting source positions in MzScheme error messages

How can I get a source location along with my error message in an
MzScheme script?

    $ cat bug.scm
    (car '())
    $ mzscheme -r bug.scm
    bash: mzscheme: command not found
    $ plt mzscheme -r bug.scm
    car: expects argument of type <pair>; given ()
    $

I'm sure this is a FAQ, but the MzScheme folks seem to quite admirably
forgo having a FAQ document in favor of having organized and current
manuals.  I'm happy to read, but I've not found anything.