diff --git a/AST.cs b/AST.cs
index 19f12e1..fdef6a3 100644
--- a/AST.cs
+++ b/AST.cs
@@ -614,7 +614,7 @@ namespace langtest
         {
             List<long> box = boxes[boxId].Item1;
             byte[] data=box.Skip((int)offset).Take((int)len).Select<long,byte>((e)=>{
-                return (byte)(e % byte.MaxValue);
+                return (byte)(e % 256);
             }).ToArray();
             
             GetStream(streamId).Write(data,0,data.Length);