Sighup doesnt work for reloading conf

Hi,
I'm using logstash 2.3.0 on my linux machine.
I change one of the conf files in the conf.d folder and then i send a sighup signal with the kill command.
Logstash doesnt seem to reload the configuration. However, when i use the --auto-reload flag it works like a charm.

What am I missing?
Thanks.