diff --git a/libavcodec/thread.h b/libavcodec/thread.h
index 540135fbc9..87bf154da9 100644
--- a/libavcodec/thread.h
+++ b/libavcodec/thread.h
@@ -129,7 +129,7 @@ int ff_thread_get_buffer(AVCodecContext *avctx, ThreadFrame *f, int flags);
  */
 void ff_thread_release_buffer(AVCodecContext *avctx, ThreadFrame *f);
 
-int ff_thread_ref_frame(ThreadFrame *dst, ThreadFrame *src);
+int ff_thread_ref_frame(ThreadFrame *dst, const ThreadFrame *src);
 
 int ff_thread_init(AVCodecContext *s);
 int ff_slice_thread_execute_with_mainfunc(AVCodecContext *avctx,
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index d93a0953fa..4f2e1649f0 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -1852,7 +1852,7 @@ unsigned int avpriv_toupper4(unsigned int x)
 ((unsigned)av_toupper((x >> 24) & 0xFF) << 24);
 }
 
-int ff_thread_ref_frame(ThreadFrame *dst, ThreadFrame *src)
+int ff_thread_ref_frame(ThreadFrame *dst, const ThreadFrame *src)
 {
     int ret;