diff --git a/include/hardware/audio.h b/include/hardware/audio.h
index 01d79b2..0a917e2 100644
--- a/include/hardware/audio.h
+++ b/include/hardware/audio.h
@@ -291,7 +291,7 @@
 /**
  * return the frame size (number of bytes per sample).
  */
-static inline size_t audio_stream_frame_size(struct audio_stream *s)
+static inline size_t audio_stream_frame_size(const struct audio_stream *s)
 {
     size_t chan_samp_sz;