diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
index a6b52e0016..533f37b460 100644
--- a/libavcodec/diracdec.c
+++ b/libavcodec/diracdec.c
@@ -799,7 +799,10 @@ static void decode_lowdelay(DiracContext *s)
             slice_num++;
 
             buf     += bytes;
-            bufsize -= bytes*8;
+            if (bufsize/8 >= bytes)
+                bufsize -= bytes*8;
+            else
+                bufsize = 0;
         }
 
     avctx->execute(avctx, decode_lowdelay_slice, slices, NULL, slice_num,