diff --git a/websocket-sharp/Ext.cs b/websocket-sharp/Ext.cs
index dd3342fd..257cdba5 100644
--- a/websocket-sharp/Ext.cs
+++ b/websocket-sharp/Ext.cs
@@ -251,6 +251,17 @@ namespace WebSocketSharp
                : null;
     }
 
+    internal static string CheckIfValidCloseParameters (this ushort code, string reason)
+    {
+      return !code.IsCloseStatusCode ()
+             ? "An invalid close status code."
+             : code.IsNoStatusCode () && !reason.IsNullOrEmpty ()
+               ? "NoStatusCode cannot have a reason."
+               : !reason.IsNullOrEmpty () && Encoding.UTF8.GetBytes (reason).Length > 123
+                 ? "A reason has greater than the allowable max size."
+                 : null;
+    }
+
     internal static string CheckIfValidCloseStatusCode (this ushort code)
     {
       return !code.IsCloseStatusCode ()