Do not log "directory index of /foo/bar/ is forbidden"

[basti]

Hello,

I have found "conditional logging"  in
http://nginx.org/en/docs/http/ngx_http_log_module.html
It seems that it only works on status codes.

Is there a way to disable logging for something like:

2015/07/09 11:02:30 [error] 24928#0: *97983 directory index of
"/foo/bar/" is forbidden, client: xx.xxx.xx.xx, server: www.example.com,
request: "GET / HTTP/1.1", host: "www.example.com"

nginx version: nginx/1.9.1

Best Regards,
basti