diff --git a/src/dec/frame.c b/src/dec/frame.c
index b41b6b42..23ae2f65 100644
--- a/src/dec/frame.c
+++ b/src/dec/frame.c
@@ -814,7 +814,7 @@ static void InitIo(VP8Decoder* const dec, VP8Io* io) {
   io->a = NULL;
 }
 
-int VP8InitFrame(VP8Decoder* const dec, VP8Io* io) {
+int VP8InitFrame(VP8Decoder* const dec, VP8Io* const io) {
   if (!InitThreadContext(dec)) return 0;  // call first. Sets dec->num_caches_.
   if (!AllocateMemory(dec)) return 0;
   InitIo(dec, io);
diff --git a/src/dec/vp8i.h b/src/dec/vp8i.h
index 8db6ab51..83a0174f 100644
--- a/src/dec/vp8i.h
+++ b/src/dec/vp8i.h
@@ -280,7 +280,7 @@ int VP8ParseIntraModeRow(VP8BitReader* const br, VP8Decoder* const dec);
 void VP8ParseQuant(VP8Decoder* const dec);
 
 // in frame.c
-int VP8InitFrame(VP8Decoder* const dec, VP8Io* io);
+int VP8InitFrame(VP8Decoder* const dec, VP8Io* const io);
 // Call io->setup() and finish setting up scan parameters.
 // After this call returns, one must always call VP8ExitCritical() with the
 // same parameters. Both functions should be used in pair. Returns VP8_STATUS_OK