diff --git a/include/system/audio.h b/include/system/audio.h
index d246070a2..da235dd1b 100644
--- a/include/system/audio.h
+++ b/include/system/audio.h
@@ -239,6 +239,7 @@ enum {
 
     AUDIO_CHANNEL_IN_MONO   = AUDIO_CHANNEL_IN_FRONT,
     AUDIO_CHANNEL_IN_STEREO = (AUDIO_CHANNEL_IN_LEFT | AUDIO_CHANNEL_IN_RIGHT),
+    AUDIO_CHANNEL_IN_FRONT_BACK = (AUDIO_CHANNEL_IN_FRONT | AUDIO_CHANNEL_IN_BACK),
     AUDIO_CHANNEL_IN_ALL    = (AUDIO_CHANNEL_IN_LEFT |
                                AUDIO_CHANNEL_IN_RIGHT |
                                AUDIO_CHANNEL_IN_FRONT |