Nginx overwrites general symfony errors with 502 Bad Gateway -

when try access non-existing route or make mistake inside twig template, instead of getting symfony error page debug information, redirected default nginx 502 bad gateway.

the log shows interesting line:

013/07/17 16:11:41 [error] 16952#0: *187 upstream sent big header while reading response header upstream, client: 127.0.0.1, server: ftwo.localhost, request: "get     /heasd http/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "ftwo.localhost" 

any ideas?

increase buffer size in nginx configuration , restart nginx afterwards suggested here.

proxy_buffer_size 128k; proxy_buffers 4 256k; proxy_busy_buffers_size 256k; 

further increase fastcgi buffer in php section of configuration ( location ~ .php$ )

fastcgi_buffer_size 128k; fastcgi_buffers 4 256k; fastcgi_busy_buffers_size 256k; 

referenced answer question codeigniter user here.