WordPress taking over actual folder

I’ve got an install that is using /%postname%/ for the permalink format, but there’s a folder called “private” that is a separate, password-protected directory containing non-wordpress HTML files and images that needs to be accessed on a regular basis.

The problem I’m having is that WordPress has taken over the /private/ URL and now it thinks it’s a slug. There are no pages on the site with a slug of “private”, so it shows a 404 error.

Since it is an actual folder and not a slug, I want WordPress to ignore the /private/ folder and let it be accessed like a normal folder.

This is the current .htaccess in the root directory (where WP is installed):

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

I’ve tried adding the following, which did absolutely nothing:

RewriteCond %{REQUEST_URI}!^/(private)/

Does anyone have any ideas? These folks need to be able to access their private folder.