diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c
index a89cbd3896..ca9194f576 100644
--- a/libavcodec/smacker.c
+++ b/libavcodec/smacker.c
@@ -246,7 +246,7 @@ static int smacker_decode_header_tree(SmackVContext *smk, GetBitContext *gb, int
     ctx.recode2 = tmp2.values;
     ctx.last = last;
 
-    huff.length = ((size + 3) >> 2) + 3;
+    huff.length = ((size + 3) >> 2) + 4;
     huff.maxlength = 0;
     huff.current = 0;
     huff.values = av_mallocz(huff.length * sizeof(int));