Prevent nginx caching empty pages?

Hi,

I’m trying to diagnose a problem we have on a rather complex system with
an nginx acting as a remote proxy server, where what appears to be a
completely empty response is being returned, seemingly from the nginx
cache. It’s early days yet in my troubleshooting, so this may not
actually be the problem, but just in case, I have two questions:

  1. Is this actually possible? Will nginx actually cache an empty
    response? (I am not sure how an empty response could actually come from
    the back end without being marked with some kind of error response
    header, which would presumably prevent any caching, but that’s a
    different issue).

  2. If it is possible, is there any way to prevent it from happening?
    E.g., setting some kind of minimal cachable size for the cache? This is
    using the now rather ancient version 0.7.65, I’m afraid.

John M