diff --git a/websocket-sharp/Net/EndPointManager.cs b/websocket-sharp/Net/EndPointManager.cs
index bc6a2787..d1c1f63e 100644
--- a/websocket-sharp/Net/EndPointManager.cs
+++ b/websocket-sharp/Net/EndPointManager.cs
@@ -85,10 +85,10 @@ namespace WebSocketSharp.Net
 
       var path = pref.Path;
       if (path.IndexOf ('%') != -1)
-        throw new HttpListenerException (87, "Invalid path.");
+        throw new HttpListenerException (87, "Includes an invalid path.");
 
       if (path.IndexOf ("//", StringComparison.Ordinal) != -1)
-        throw new HttpListenerException (87, "Invalid path.");
+        throw new HttpListenerException (87, "Includes an invalid path.");
 
       // Listens on all the interfaces if host name cannot be parsed by IPAddress.
       getEndPointListener (pref, listener).AddPrefix (pref, listener);