I kept seeing “upstream sent unsupported FastCGI protocol version” in
my error logs, and they went away when I turned fastcgi_cache off.
It turned out that the files holding the cache were corrupted,
starting at random places instead of the FastCGI headers.
After trying to tweak things every possible way, I finally found out
that the errors seemed to go away if I didn’t use
And later on, I realized that when using fastcgi_no_cache with the
same variable as for fastcgi_cache_bypass, I don’t get any of those
errors, and it works as intended.
I saw in the source that a warning was added recommending to use
fastcgi_cache_bypass when fastcgi_no_cache is used, but not the other
Should they always be used together, or is this a bug ?