[Red Hat Enterprise Linux WS release 3 (Taroon Update 4)]
[Linux 2.4.21-27.0.2.EL i686 i686 i386 GNU/Linux]
[Server version: Apache/2.0.46]

Accessing http://localhost/index works ok.
Accessing http://localhost/ does not work:

404 Not Found - The requested URL /index was not found on this server.
Apache/2.0.46 (Red Hat) Server at localhost Port 80.

error_log reads:
[error] [client 127.0.0.1] Attempt to serve directory: /var/www/html/

$ apachectl configtest
Syntax OK

http://httpd.apache.org/docs-2.0/mod/mod_dir.html says the
DirectorySlash Directive is available in version 2.0.51 and later.
Should I upgrade?

Snipped relevant sections from httpd.conf:

LoadModule dir_module modules/mod_dir.so
DocumentRoot "/var/www/html"
<Directory "/var/www/html">
Options Indexes FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
</Directory>
DirectoryIndex index index.html

The file /var/www/html/index exists and is readable.

Please help me point out why "trailing slash" redirect does not work.

--
S.T.