how to ensure 5xx pages served by nginx dont get cached by users?

[nginx.mailinglist]

I noticed that under heavy loads nginx returns a default 5xx response (503)
Anyways sometimes users email me saying they encountered the error and it
wont go away, me telling them to clear their browser cache usually solves
the issue, so that leads me to believe these pages are cached

Am i missing something is there an option to make nginx return "no cache"
headers along with a default 5xx error message?

Using nginx 0.6.32 on a few dozen Suse 10.* and 11.* servers with php5.2.6
and php-fpm patch

Oh and thank you :)
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