Gear VR and External Microphone

I am trying to use an external headset microphone with an application that I am developing but when I am using the app inside the Gear VR, the inbuilt microphone is used instead. The external microphone works if I use the development mode and run the app outside of the Gear device but as soon as I plug it in, the inbuilt microphone is used.
Is there a known work around for this issue?
This is with the Samsung S6 and building using 5.2.1p3