diff --git a/websocket-sharp/Net/HttpListener.cs b/websocket-sharp/Net/HttpListener.cs
index c8334987..07970e14 100644
--- a/websocket-sharp/Net/HttpListener.cs
+++ b/websocket-sharp/Net/HttpListener.cs
@@ -352,7 +352,7 @@ namespace WebSocketSharp.Net
     public ServerSslConfiguration SslConfiguration {
       get {
         CheckDisposed ();
-        return _sslConfig ?? (_sslConfig = new ServerSslConfiguration (null));
+        return _sslConfig ?? (_sslConfig = new ServerSslConfiguration ());
       }
 
       set {
diff --git a/websocket-sharp/Net/ServerSslConfiguration.cs b/websocket-sharp/Net/ServerSslConfiguration.cs
index c10b4dc1..e52d33df 100644
--- a/websocket-sharp/Net/ServerSslConfiguration.cs
+++ b/websocket-sharp/Net/ServerSslConfiguration.cs
@@ -79,6 +79,22 @@ namespace WebSocketSharp.Net
     {
     }
 
+    /// <summary>
+    /// Copies the parameters from the specified <paramref name="configuration"/> to
+    /// a new instance of the <see cref="ServerSslConfiguration"/> class.
+    /// </summary>
+    /// <param name="configuration">
+    /// A <see cref="ServerSslConfiguration"/> from which to copy.
+    /// </param>
+    public ServerSslConfiguration (ServerSslConfiguration configuration)
+    {
+      _checkCertRevocation = configuration._checkCertRevocation;
+      _clientCertRequired = configuration._clientCertRequired;
+      _clientCertValidationCallback = configuration._clientCertValidationCallback;
+      _enabledSslProtocols = configuration._enabledSslProtocols;
+      _serverCert = configuration._serverCert;
+    }
+
     /// <summary>
     /// Initializes a new instance of the <see cref="ServerSslConfiguration"/> class
     /// with the specified <paramref name="serverCertificate"/>,
diff --git a/websocket-sharp/Server/WebSocketServer.cs b/websocket-sharp/Server/WebSocketServer.cs
index 92b07495..e2829f35 100644
--- a/websocket-sharp/Server/WebSocketServer.cs
+++ b/websocket-sharp/Server/WebSocketServer.cs
@@ -583,7 +583,7 @@ namespace WebSocketSharp.Server
     public ServerSslConfiguration SslConfiguration {
       get {
         if (_sslConfig == null)
-          _sslConfig = new ServerSslConfiguration (null);
+          _sslConfig = new ServerSslConfiguration ();
 
         return _sslConfig;
       }