diff --git a/websocket-sharp/Ext.cs b/websocket-sharp/Ext.cs
index 8b2255e1..f0d27a08 100644
--- a/websocket-sharp/Ext.cs
+++ b/websocket-sharp/Ext.cs
@@ -852,10 +852,6 @@ namespace WebSocketSharp
       this string uriString, out Uri result, out string message)
     {
       result = null;
-      if (uriString.Length == 0) {
-        message = "An empty string.";
-        return false;
-      }
 
       var uri = uriString.ToUri ();
       if (!uri.IsAbsoluteUri) {
diff --git a/websocket-sharp/Server/WebSocketServer.cs b/websocket-sharp/Server/WebSocketServer.cs
index 7e6d6f23..4630f5f7 100644
--- a/websocket-sharp/Server/WebSocketServer.cs
+++ b/websocket-sharp/Server/WebSocketServer.cs
@@ -144,6 +144,9 @@ namespace WebSocketSharp.Server
       if (url == null)
         throw new ArgumentNullException ("url");
 
+      if (url.Length == 0)
+        throw new ArgumentException ("An empty string.", "url");
+
       string msg;
       if (!tryCreateUri (url, out _uri, out msg))
         throw new ArgumentException (msg, "url");
diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index dbae1c6e..e8a79b24 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -180,6 +180,9 @@ namespace WebSocketSharp
       if (url == null)
         throw new ArgumentNullException ("url");
 
+      if (url.Length == 0)
+        throw new ArgumentException ("An empty string.", "url");
+
       string msg;
       if (!url.TryCreateWebSocketUri (out _uri, out msg))
         throw new ArgumentException (msg, "url");