diff --git a/libavcodec/shorten.c b/libavcodec/shorten.c
index 833a817561..22fdcff403 100644
--- a/libavcodec/shorten.c
+++ b/libavcodec/shorten.c
@@ -156,7 +156,7 @@ static void fix_bitshift(ShortenContext *s, int32_t *buffer)
 
     if (s->bitshift != 0)
         for (i = 0; i < s->blocksize; i++)
-            buffer[s->nwrap + i] <<= s->bitshift;
+            buffer[i] <<= s->bitshift;
 }