diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index f5021208c3..610e365c36 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -610,7 +610,7 @@ static inline int get_amv(Mpeg4DecContext *ctx, int n)
             dy -= 1 << (shift + a + 1);
         else
             dx -= 1 << (shift + a + 1);
-        mb_v = s->sprite_offset[0][n] + dx * s->mb_x * 16 + dy * s->mb_y * 16;
+        mb_v = s->sprite_offset[0][n] + dx * s->mb_x * 16U + dy * s->mb_y * 16U;
 
         sum = 0;
         for (y = 0; y < 16; y++) {