diff --git a/libavcodec/a64enc.h b/libavcodec/a64enc.h
index bf5eb02cd1..d5f8e9ac99 100644
--- a/libavcodec/a64enc.h
+++ b/libavcodec/a64enc.h
@@ -41,7 +41,7 @@ typedef struct A64Context {
     AVLFG randctx;
     int mc_lifetime;
     int mc_use_5col;
-    int mc_frame_counter;
+    unsigned mc_frame_counter;
     int *mc_meta_charset;
     int *mc_charmap;
     int *mc_best_cb;