diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index a24547b81c..a4ed1f8b36 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -469,7 +469,7 @@ static void backup_duplicate_context(MpegEncContext *bak, MpegEncContext *src)
 #undef COPY
 }
 
-int ff_update_duplicate_context(MpegEncContext *dst, MpegEncContext *src)
+int ff_update_duplicate_context(MpegEncContext *dst, const MpegEncContext *src)
 {
     MpegEncContext bak;
     int i, ret;
diff --git a/libavcodec/mpegvideo.h b/libavcodec/mpegvideo.h
index d96cd7f1ec..77d1593928 100644
--- a/libavcodec/mpegvideo.h
+++ b/libavcodec/mpegvideo.h
@@ -589,7 +589,7 @@ void ff_mpv_reconstruct_mb(MpegEncContext *s, int16_t block[12][64]);
 
 void ff_clean_intra_table_entries(MpegEncContext *s);
 
-int ff_update_duplicate_context(MpegEncContext *dst, MpegEncContext *src);
+int ff_update_duplicate_context(MpegEncContext *dst, const MpegEncContext *src);
 void ff_set_qscale(MpegEncContext * s, int qscale);
 
 void ff_mpv_idct_init(MpegEncContext *s);
diff --git a/libavcodec/mpegvideo_enc.c b/libavcodec/mpegvideo_enc.c
index 9c2243eed7..5c8e13947f 100644
--- a/libavcodec/mpegvideo_enc.c
+++ b/libavcodec/mpegvideo_enc.c
@@ -250,7 +250,7 @@ void ff_init_qscale_tab(MpegEncContext *s)
 }
 
 static void update_duplicate_context_after_me(MpegEncContext *dst,
-                                              MpegEncContext *src)
+                                              const MpegEncContext *src)
 {
 #define COPY(a) dst->a= src->a
     COPY(pict_type);