diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index 80366ec3..149de430 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -3876,7 +3876,7 @@ namespace WebSocketSharp
     public void SendAsync (string data, Action<bool> completed)
     {
       if (_readyState != WebSocketState.Open) {
-        var msg = "The current state of the interface is not Open.";
+        var msg = "The SendAsync method is not available.";
 
         throw new InvalidOperationException (msg);
       }