Logstash filter plugin, import dependency

I am having a problem with custom filter and importing dependencies. Can anyone help me please! I get "Attempting to load the X filter plugin resulted in this error: No such file to load - memcache". The code "requires" memcache. This is available as if I were doing it in any other script and run it in the CLI, does it only work if logstash is not running? Is it using some kind of linked ruby ​​or smth with a different import path? Its 1.4.2 on Debian, if that matters. Driving me insane (Im not a ruby ​​hacker so I spin my wheels a little).