Apache's trailing slash and proxying to RESTful apps

I have a somewhat odd case with the Web app I just deployed today (no, not Rails, it's Merb!). I have a RESTful Documents controller which needs to receive POST requests on /documents. I also have a documents directory in the public document root. The whole thing is hosted behind Apache with mod_proxy_balancer, and mod_rewrite to let Apache serve static files (all as described on the Mongrel site).

So when I would POST to /documents, Apache in its (normally quite useful) wisdom decided to rewrite it to /documents/ and (worse) to change the request to a GET. This is because of mod_dir, which provides the DirectoryIndex directive and the (less well-known) DirectorySlash directive, which defaults to On. So to fix it, I just set DirectorySlash to Off for the documents directory, and bingo, it works.

Now, if I needed directory indexes on the subdirectories of the public/documents/ directory, I'd have to work around, but this is fine for my current setup.