diff --git a/websocket-sharp/Net/HttpUtility.cs b/websocket-sharp/Net/HttpUtility.cs
index 45c9b8f3..6772f666 100644
--- a/websocket-sharp/Net/HttpUtility.cs
+++ b/websocket-sharp/Net/HttpUtility.cs
@@ -404,6 +404,14 @@ namespace WebSocketSharp.Net
       return c >= '0' && c <= '9';
     }
 
+    private static bool isUnreserved (char c)
+    {
+      return c == '*'
+             || c == '-'
+             || c == '.'
+             || c == '_';
+    }
+
     private static bool notEncoded (char c)
     {
       return c == '!' ||