diff --git a/websocket-sharp/Ext.cs b/websocket-sharp/Ext.cs
index b1c09412..09df2fa8 100644
--- a/websocket-sharp/Ext.cs
+++ b/websocket-sharp/Ext.cs
@@ -510,9 +510,9 @@ namespace WebSocketSharp
     }
 
     internal static TcpListenerWebSocketContext GetWebSocketContext (
-      this TcpClient client, X509Certificate cert, bool secure, Logger logger)
+      this TcpClient client, string protocol, X509Certificate cert, bool secure, Logger logger)
     {
-      return new TcpListenerWebSocketContext (client, cert, secure, logger);
+      return new TcpListenerWebSocketContext (client, protocol, cert, secure, logger);
     }
 
     internal static bool IsCompressionExtension (this string value)
diff --git a/websocket-sharp/Net/HttpListenerContext.cs b/websocket-sharp/Net/HttpListenerContext.cs
index 60db71a1..290e7fc6 100644
--- a/websocket-sharp/Net/HttpListenerContext.cs
+++ b/websocket-sharp/Net/HttpListenerContext.cs
@@ -204,12 +204,34 @@ namespace WebSocketSharp.Net
     /// A <see cref="HttpListenerWebSocketContext"/> that represents the WebSocket connection
     /// request.
     /// </returns>
+    /// <param name="protocol">
+    /// A <see cref="string"/> that represents the subprotocol used in the WebSocket connection.
+    /// </param>
     /// <param name="logger">
     /// A <see cref="Logger"/> that provides the logging functions used in the WebSocket attempts.
     /// </param>
-    public HttpListenerWebSocketContext AcceptWebSocket (Logger logger)
+    /// <exception cref="ArgumentException">
+    ///   <para>
+    ///   <paramref name="protocol"/> is empty.
+    ///   </para>
+    ///   <para>
+    ///   -or-
+    ///   </para>
+    ///   <para>
+    ///   <paramref name="protocol"/> contains an invalid character.
+    ///   </para>
+    /// </exception>
+    public HttpListenerWebSocketContext AcceptWebSocket (string protocol, Logger logger)
     {
-      return new HttpListenerWebSocketContext (this, logger);
+      if (protocol != null) {
+        if (protocol.Length == 0)
+          throw new ArgumentException ("An empty string.", "protocol");
+
+        if (!protocol.IsToken ())
+          throw new ArgumentException ("Contains an invalid character.", "protocol");
+      }
+
+      return new HttpListenerWebSocketContext (this, protocol, logger ?? new Logger ());
     }
 
     #endregion
diff --git a/websocket-sharp/Net/WebSockets/HttpListenerWebSocketContext.cs b/websocket-sharp/Net/WebSockets/HttpListenerWebSocketContext.cs
index a6e7d01e..f1c2c2ff 100644
--- a/websocket-sharp/Net/WebSockets/HttpListenerWebSocketContext.cs
+++ b/websocket-sharp/Net/WebSockets/HttpListenerWebSocketContext.cs
@@ -51,11 +51,12 @@ namespace WebSocketSharp.Net.WebSockets
 
     #region Internal Constructors
 
-    internal HttpListenerWebSocketContext (HttpListenerContext context, Logger logger)
+    internal HttpListenerWebSocketContext (
+      HttpListenerContext context, string protocol, Logger logger)
     {
       _context = context;
       _stream = WsStream.CreateServerStream (context);
-      _websocket = new WebSocket (this, logger ?? new Logger ());
+      _websocket = new WebSocket (this, protocol, logger);
     }
 
     #endregion
diff --git a/websocket-sharp/Net/WebSockets/TcpListenerWebSocketContext.cs b/websocket-sharp/Net/WebSockets/TcpListenerWebSocketContext.cs
index 44b60cb2..3f364e9f 100644
--- a/websocket-sharp/Net/WebSockets/TcpListenerWebSocketContext.cs
+++ b/websocket-sharp/Net/WebSockets/TcpListenerWebSocketContext.cs
@@ -59,7 +59,7 @@ namespace WebSocketSharp.Net.WebSockets
     #region Internal Constructors
 
     internal TcpListenerWebSocketContext (
-      TcpClient client, X509Certificate cert, bool secure, Logger logger)
+      TcpClient client, string protocol, X509Certificate cert, bool secure, Logger logger)
     {
       _client = client;
       _secure = secure;
@@ -67,7 +67,7 @@ namespace WebSocketSharp.Net.WebSockets
       _request = _stream.ReadHandshake<HandshakeRequest> (
         HandshakeRequest.Parse, 90000);
 
-      _websocket = new WebSocket (this, logger);
+      _websocket = new WebSocket (this, protocol, logger);
     }
 
     #endregion
diff --git a/websocket-sharp/Server/HttpServer.cs b/websocket-sharp/Server/HttpServer.cs
index a3886539..19e14a6e 100644
--- a/websocket-sharp/Server/HttpServer.cs
+++ b/websocket-sharp/Server/HttpServer.cs
@@ -489,7 +489,7 @@ namespace WebSocketSharp.Server
               return;
 
             if (context.Request.IsUpgradeTo ("websocket")) {
-              acceptWebSocketRequest (context.AcceptWebSocket (_logger));
+              acceptWebSocketRequest (context.AcceptWebSocket (null, _logger));
               return;
             }
 
diff --git a/websocket-sharp/Server/WebSocketServer.cs b/websocket-sharp/Server/WebSocketServer.cs
index 0f69ee98..c6996d77 100644
--- a/websocket-sharp/Server/WebSocketServer.cs
+++ b/websocket-sharp/Server/WebSocketServer.cs
@@ -476,7 +476,7 @@ namespace WebSocketSharp.Server
       ThreadPool.QueueUserWorkItem (
         state => {
           try {
-            var context = client.GetWebSocketContext (_cert, _secure, _logger);
+            var context = client.GetWebSocketContext (null, _cert, _secure, _logger);
             if (_authSchemes != AuthenticationSchemes.Anonymous &&
                 !authenticateRequest (_authSchemes, context))
               return;
diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index 0f1ad645..da34a715 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -106,9 +106,10 @@ namespace WebSocketSharp
     #region Internal Constructors
 
     // As server
-    internal WebSocket (HttpListenerWebSocketContext context, Logger logger)
+    internal WebSocket (HttpListenerWebSocketContext context, string protocol, Logger logger)
     {
       _context = context;
+      _protocol = protocol;
       _logger = logger;
 
       _closeContext = context.Close;
@@ -120,9 +121,10 @@ namespace WebSocketSharp
     }
 
     // As server
-    internal WebSocket (TcpListenerWebSocketContext context, Logger logger)
+    internal WebSocket (TcpListenerWebSocketContext context, string protocol, Logger logger)
     {
       _context = context;
+      _protocol = protocol;
       _logger = logger;
 
       _closeContext = context.Close;