Problems loading directory URLs

[Jimmy Theis]

I'm new to Varnish and am attempting to use the stock settings for the 
FreeBSD ports distribution of the program. So far I'm very happy with 
the performance increase I've seen, even without digging down and 
tuning, but there is one bit of strange behavior I'm struggling with:

When the url of a directory is requested without a / following it, the 
request fails and nothing is returned. However, in all other situations, 
including appending the final / to the url, Varnish handles it correctly.

I'm running Apache for Subversion and PHP handling, with nginx on top of 
that as a proxy and for hosting static files. Nginx serves on port 8000 
and Varnish uses it as its backend. The URL weirdness occurs both when 
accessing a directory that nginx serves up and directories inside 
Subversion repositories that Apache serves. This behavior is not present 
when nginx is listening directly to port 80.

I'm happy to provide extra information if need be. This is a server for 
personal projects, so I'm fine tinkering with it if it helps solve the 
problem.

Thanks in advance,
Jimmy