Alternatively, if one has no desire for directory indexes *anywhere* on the site, (and one is running with a DSO-enabled Apache) simply uncomment the LoadModule line (and AddModule line, if present) for mod_autoindex and bounce Apache. This has the added benefit of reducing the number of modules Apache loads, which is generally a good idea. Not that removing them arbitrarily is a good idea, but removing ones you know you're not going to need is.
Of course, this assumes you have write access to Apache's configuration file. =)