Lighttpd

I'm trying to set up Trac using the instructions at http://redmine.lighttpd.net/wiki/1/HowToSetupTrac, but as soon as I add the mod_alias line I get an error something along the lines of:

Starting lighttpd: 2008-12-22 06:41:48: (plugin.c.165) dlopen() failed for: /usr/local/lib/mod_indexfile, mod_alias.so /usr/local/lib/mod_indexfile, mod_alias.so: cannot open shared object file: No such file or directory 

I've seen a couple of different combinations, but it basically looks like it's trying to find a file that's a combination of two mod names.

Adding:

    fastcgi.server+= ("/trac" =>
                   ("trac" =>
                     ("socket" => "/tmp/trac-fastcgi.sock",
                      "bin-path" => "/usr/lib/python2.3/site-packages/Trac-0.11.2.1-py2.3.egg/trac/web/fcgi_frontend.py",
                      "check-local" => "disable",
                      "bin-environment" =>
                        ("TRAC_ENV_PARENT_DIR" => "/data/trac/")
                     )
                   )
                 )

works fine, and trac will install okay. As soon as I add:

  # Aliasing functionality is needed
  #server.modules = ("mod_alias")

or

  # Aliasing functionality is needed
  #server.modules+= ("mod_alias")

before it then I get the error above and Lighty won't start.

I've compiled 1.20 from source on a CentOS 4.6 box, but all of the modules are there and the ones I'm already using work okay.

Anyone know what might be causing it to fail to load modules as soon as I add mod_alias?

Thanks.