diff --git a/websocket-sharp/Net/HttpResponseHeader.cs b/websocket-sharp/Net/HttpResponseHeader.cs
index 822e4a9d..d32afe6c 100644
--- a/websocket-sharp/Net/HttpResponseHeader.cs
+++ b/websocket-sharp/Net/HttpResponseHeader.cs
@@ -8,7 +8,7 @@
  * The MIT License
  *
  * Copyright (c) 2005 Novell, Inc. (http://www.novell.com)
- * Copyright (c) 2014 sta.blockhead
+ * Copyright (c) 2014-2020 sta.blockhead
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal