diff --git a/media/libnbaio/NBAIO.cpp b/media/libnbaio/NBAIO.cpp
index 26ef8c4..51514de 100644
--- a/media/libnbaio/NBAIO.cpp
+++ b/media/libnbaio/NBAIO.cpp
@@ -28,11 +28,12 @@
     return Format_channelCount(format) * sizeof(short);
 }
 
-size_t Format_frameBitShift(const NBAIO_Format& format)
+int Format_frameBitShift(const NBAIO_Format& format)
 {
     // FIXME The sample format is hard-coded to AUDIO_FORMAT_PCM_16_BIT
     // sizeof(short) == 2, so frame size == 1 << channels
     return Format_channelCount(format);
+    // FIXME must return -1 for non-power of 2
 }
 
 const NBAIO_Format Format_Invalid = { 0 };