PHP-FPM doesn't write to error log

http://stackoverflow.com/questions/8677493/php-fpm-doesnt-write-to-error-log

PHP-FPM.conf:

; Redirect worker stdout and stderr into main error log. If not set, stdout and
; stderr will be redirected to /dev/null according to FastCGI specs.
; Default Value: no
catch_workers_output = yes