Since update to 2016 unity integration I'm getting an error with GetRTPCValue

Question

I'm using GetRTPCValue to get the initial setting of the SFX and Music volume RTPCs, but since ive updated I'm getting the error 

No overload for method `GetRTPCValue' takes `4' arguments​

Looking at the documentation, it doesn't seem to have changed, so what am I doing wrong?

heres my code: 

int type1 = (int)RTPCValue_type.RTPCValue_GameObject;
AkSoundEngine.GetRTPCValue("SFX_Volume", gameObject, out sfxVol, ref type1);