diff --git a/libavcodec/cscd.c b/libavcodec/cscd.c
index 36005a17b8..4d99d960a7 100644
--- a/libavcodec/cscd.c
+++ b/libavcodec/cscd.c
@@ -135,7 +135,7 @@ static void add_frame_32(AVFrame *f, uint8_t *src,
 #endif
 
 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,
-                        uint8_t *buf, int buf_size) {
+                        const uint8_t *buf, int buf_size) {
     CamStudioContext *c = avctx->priv_data;
     AVFrame *picture = data;