diff --git a/libavformat/flacenc.h b/libavformat/flacenc.h
index d5d53a5dcb..b308d0d021 100644
--- a/libavformat/flacenc.h
+++ b/libavformat/flacenc.h
@@ -26,7 +26,7 @@
 #include "libavcodec/bytestream.h"
 #include "avformat.h"
 
-int ff_flac_write_header(AVIOContext *pb, uint8_t *extradata,
+int ff_flac_write_header(AVIOContext *pb, const uint8_t *extradata,
                          int extradata_size, int last_block);
 
 int ff_flac_is_native_layout(uint64_t channel_layout);
diff --git a/libavformat/flacenc_header.c b/libavformat/flacenc_header.c
index 61833cc8b9..aba22a59d8 100644
--- a/libavformat/flacenc_header.c
+++ b/libavformat/flacenc_header.c
@@ -26,7 +26,7 @@
 #include "avformat.h"
 #include "flacenc.h"
 
-int ff_flac_write_header(AVIOContext *pb, uint8_t *extradata,
+int ff_flac_write_header(AVIOContext *pb, const uint8_t *extradata,
                          int extradata_size, int last_block)
 {
     uint8_t header[8] = {