diff --git a/websocket-sharp/Net/HttpUtility.cs b/websocket-sharp/Net/HttpUtility.cs
index 0401a75d..53129b24 100644
--- a/websocket-sharp/Net/HttpUtility.cs
+++ b/websocket-sharp/Net/HttpUtility.cs
@@ -51,7 +51,7 @@ using System.Text;
 
 namespace WebSocketSharp.Net
 {
-  internal sealed class HttpUtility
+  internal static class HttpUtility
   {
     #region Private Fields