Zabbix 2.0 log monitoring - deactivating trigger

I am using Zabbix for monitoring log files. I've got trigger, which is activated when errors are written to the log:

{Test:log["/opt/test/log.out","^ERROR.*$","UTF-8",100].diff(0)}>0

So, now I acknowledge that, problems are solved, but trigger stays on.

How can one handle this?