diff --git a/libavcodec/ffv1.c b/libavcodec/ffv1.c
index a27eca5ae3..d8a0c39254 100644
--- a/libavcodec/ffv1.c
+++ b/libavcodec/ffv1.c
@@ -63,7 +63,7 @@ av_cold int ff_ffv1_common_init(AVCodecContext *avctx)
     return 0;
 }
 
-av_cold int ff_ffv1_init_slice_state(FFV1Context *f, FFV1Context *fs)
+av_cold int ff_ffv1_init_slice_state(const FFV1Context *f, FFV1Context *fs)
 {
     int j, i;
 
@@ -170,7 +170,7 @@ int ff_ffv1_allocate_initial_states(FFV1Context *f)
     return 0;
 }
 
-void ff_ffv1_clear_slice_state(FFV1Context *f, FFV1Context *fs)
+void ff_ffv1_clear_slice_state(const FFV1Context *f, FFV1Context *fs)
 {
     int i, j;
 
diff --git a/libavcodec/ffv1.h b/libavcodec/ffv1.h
index 473780c876..8ffe5ab433 100644
--- a/libavcodec/ffv1.h
+++ b/libavcodec/ffv1.h
@@ -139,11 +139,11 @@ typedef struct FFV1Context {
 } FFV1Context;
 
 int ff_ffv1_common_init(AVCodecContext *avctx);
-int ff_ffv1_init_slice_state(FFV1Context *f, FFV1Context *fs);
+int ff_ffv1_init_slice_state(const FFV1Context *f, FFV1Context *fs);
 int ff_ffv1_init_slices_state(FFV1Context *f);
 int ff_ffv1_init_slice_contexts(FFV1Context *f);
 int ff_ffv1_allocate_initial_states(FFV1Context *f);
-void ff_ffv1_clear_slice_state(FFV1Context *f, FFV1Context *fs);
+void ff_ffv1_clear_slice_state(const FFV1Context *f, FFV1Context *fs);
 int ff_ffv1_close(AVCodecContext *avctx);
 
 static av_always_inline int fold(int diff, int bits)
diff --git a/libavcodec/ffv1dec.c b/libavcodec/ffv1dec.c
index 74c907a156..c6af4e9bc0 100644
--- a/libavcodec/ffv1dec.c
+++ b/libavcodec/ffv1dec.c
@@ -161,7 +161,7 @@ static int decode_plane(FFV1Context *s, uint8_t *src,
     return 0;
 }
 
-static int decode_slice_header(FFV1Context *f, FFV1Context *fs)
+static int decode_slice_header(const FFV1Context *f, FFV1Context *fs)
 {
     RangeCoder *c = &fs->c;
     uint8_t state[CONTEXT_SIZE];
@@ -974,7 +974,8 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPac
     return buf_size;
 }
 
-static void copy_fields(FFV1Context *fsdst, FFV1Context *fssrc, FFV1Context *fsrc)
+static void copy_fields(FFV1Context *fsdst, const FFV1Context *fssrc,
+                        const FFV1Context *fsrc)
 {
     fsdst->version             = fsrc->version;
     fsdst->micro_version       = fsrc->micro_version;