kAudioSessionCategory_MediaPlayback

trying to get the setup property kAudioSessionProperty_OverrideCategoryMixWithOthers to work with MediaPlayback category in AudioQueue. Ultimately I need the app to mix with other audio and play in background mode which is what the MediaPlayback category and OverrideCategoryMixWithOthers will accomplish. However, when setting the mixWithOthers property, app crashes. Any suggestions?

Mick