diff --git a/websocket-sharp/Server/WebSocketBehavior.cs b/websocket-sharp/Server/WebSocketBehavior.cs
index 2f7b9b07..a4664573 100644
--- a/websocket-sharp/Server/WebSocketBehavior.cs
+++ b/websocket-sharp/Server/WebSocketBehavior.cs
@@ -695,6 +695,70 @@ namespace WebSocketSharp.Server
       _websocket.CloseAsync (code, reason);
     }
 
+    /// <summary>
+    /// Closes the WebSocket connection for a session asynchronously with
+    /// the specified code and reason.
+    /// </summary>
+    /// <remarks>
+    ///   <para>
+    ///   This method does not wait for the close to be complete.
+    ///   </para>
+    ///   <para>
+    ///   This method does nothing if the current state of the connection is
+    ///   Closing or Closed.
+    ///   </para>
+    /// </remarks>
+    /// <param name="code">
+    ///   <para>
+    ///   One of the <see cref="CloseStatusCode"/> enum values.
+    ///   </para>
+    ///   <para>
+    ///   It represents the status code indicating the reason for the close.
+    ///   </para>
+    /// </param>
+    /// <param name="reason">
+    ///   <para>
+    ///   A <see cref="string"/> that represents the reason for the close.
+    ///   </para>
+    ///   <para>
+    ///   The size must be 123 bytes or less in UTF-8.
+    ///   </para>
+    /// </param>
+    /// <exception cref="InvalidOperationException">
+    /// The session has not started yet.
+    /// </exception>
+    /// <exception cref="ArgumentException">
+    ///   <para>
+    ///   <paramref name="code"/> is
+    ///   <see cref="CloseStatusCode.MandatoryExtension"/>.
+    ///   </para>
+    ///   <para>
+    ///   -or-
+    ///   </para>
+    ///   <para>
+    ///   <paramref name="code"/> is
+    ///   <see cref="CloseStatusCode.NoStatus"/> and there is reason.
+    ///   </para>
+    ///   <para>
+    ///   -or-
+    ///   </para>
+    ///   <para>
+    ///   <paramref name="reason"/> could not be UTF-8-encoded.
+    ///   </para>
+    /// </exception>
+    /// <exception cref="ArgumentOutOfRangeException">
+    /// The size of <paramref name="reason"/> is greater than 123 bytes.
+    /// </exception>
+    protected void CloseAsync (CloseStatusCode code, string reason)
+    {
+      if (_websocket == null) {
+        var msg = "The session has not started yet.";
+        throw new InvalidOperationException (msg);
+      }
+
+      _websocket.CloseAsync (code, reason);
+    }
+
     /// <summary>
     /// Calls the <see cref="OnError"/> method with the specified message.
     /// </summary>