Is it possible to 'duck' an AudioSession whilst using OpenAL?

Question

Does anybody know if this is possible?

I have my audio session and OpenAL set-up like so:

// Allow their music to play in the background
AudioSessionInitialize(NULL, NULL, openALInterruptionListener, (__bridge void *)(self));

UInt32 sessionCategory = kAudioSessionCategory_AmbientSound;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(sessionCategory), &sessionCategory);

UInt32 allowMixing = false;
AudioSessionSetProperty(kAudioSessionProperty_OtherMixableAudioShouldDuck, sizeof(allowMixing), &allowMixing);

//      use the device to make a context
_mContext = alcCreateContext(_mDevice, NULL);
//      set my context to the currently active one
alcMakeContextCurrent(_mContext);

And I have ducking set-up like so:

- (void)setSoundDucked:(BOOL)soundDucked
{    
    if(soundDucked)
    {
        UInt32 allowMixing = true;
        AudioSessionSetProperty(kAudioSessionProperty_OtherMixableAudioShouldDuck,     sizeof(allowMixing), &allowMixing);
        AudioSessionSetActive(false);
        AudioSessionSetActive(true);
    }
    else
    {
        UInt32 allowMixing = false;
        AudioSessionSetProperty(kAudioSessionProperty_OtherMixableAudioShouldDuck, sizeof(allowMixing), &allowMixing);
        AudioSessionSetActive(false);
        AudioSessionSetActive(true);
    }
}

However, sound doesn't duck. It will only duck if I comment out the following lines:

//      use the device to make a context
_mContext = alcCreateContext(_mDevice, NULL);
//      set my context to the currently active one
alcMakeContextCurrent(_mContext);

Is there anyway of getting OpenAL to play nice with the audio ducking property?