diff --git a/libavcodec/ccaption_dec.c b/libavcodec/ccaption_dec.c
index 6e26342c8274efe6eb7f8852e8d0420abf091f7b..e84c4800c802cd95249a3aa8296a6bda2fbb44b8 100644
--- a/libavcodec/ccaption_dec.c
+++ b/libavcodec/ccaption_dec.c
@@ -291,8 +291,8 @@ static int capture_screen(CCaptionSubContext *ctx)
     for (i = 0; screen->row_used && i < SCREEN_ROWS; i++)
     {
         if (CHECK_FLAG(screen->row_used, i)) {
-            char *row = screen->characters[i];
-            char *font = screen->fonts[i];
+            const char *row = screen->characters[i];
+            const char *font = screen->fonts[i];
             int j = 0;
 
             /* skip leading space */