[Q] "OK google" topic

Hey guys, i am using official cm11 for my GT-i9100. They have released their M-Snapshot build but still i haven't been able to figure out how to activate google now using "ok google". There is a search bar on my homescreen but it doesn't seem to be responding. So unless i go in the google app in the app drawer i can't use ok google to search. Is it just happening on my phone or is it happening on other phones as well?
Please help me. Thanks in advance