"OK Google" too sensitive, reacts on "OK" only

When I want to start an "OK Google" query, I just have to say "OK" and Google Search starts listening. Unfortunately that makes the features unusable because when on a charger my phone is always active and when anyone in the office says "OK", my phone starts searching away. Same behaviour when I start the original "Google Search" app and use the hotword. What to do? My specs: - Device: Samsung Galaxy S4 - ROM: SlimKat 6.8 - Launcher: Apex (has OK Google support) - Additinal Info: Xprivacy installed.