diff --git a/websocket-sharp/Server/WebSocketSessionManager.cs b/websocket-sharp/Server/WebSocketSessionManager.cs
index 86d6581a..3a752937 100644
--- a/websocket-sharp/Server/WebSocketSessionManager.cs
+++ b/websocket-sharp/Server/WebSocketSessionManager.cs
@@ -869,63 +869,6 @@ namespace WebSocketSharp.Server
         broadcastAsync (Opcode.Binary, new MemoryStream (bytes), completed);
     }
 
-    /// <summary>
-    /// Sends a ping with <paramref name="message"/> to every client in
-    /// the WebSocket service.
-    /// </summary>
-    /// <returns>
-    ///   <para>
-    ///   A <c>Dictionary&lt;string, bool&gt;</c>.
-    ///   </para>
-    ///   <para>
-    ///   It represents a collection of pairs of a session ID and
-    ///   a value indicating whether a pong has been received from
-    ///   the client within a time.
-    ///   </para>
-    /// </returns>
-    /// <param name="message">
-    ///   <para>
-    ///   A <see cref="string"/> that represents the message to send.
-    ///   </para>
-    ///   <para>
-    ///   The size must be 125 bytes or less in UTF-8.
-    ///   </para>
-    /// </param>
-    /// <exception cref="InvalidOperationException">
-    /// The current state of the manager is not Start.
-    /// </exception>
-    /// <exception cref="ArgumentException">
-    /// <paramref name="message"/> could not be UTF-8-encoded.
-    /// </exception>
-    /// <exception cref="ArgumentOutOfRangeException">
-    /// The size of <paramref name="message"/> is greater than 125 bytes.
-    /// </exception>
-    [Obsolete ("This method will be removed.")]
-    public Dictionary<string, bool> Broadping (string message)
-    {
-      if (_state != ServerState.Start) {
-        var msg = "The current state of the manager is not Start.";
-        throw new InvalidOperationException (msg);
-      }
-
-      if (message.IsNullOrEmpty ())
-        return Broadping (WebSocketFrame.EmptyPingBytes, _waitTime);
-
-      byte[] bytes;
-      if (!message.TryGetUTF8EncodedBytes (out bytes)) {
-        var msg = "It could not be UTF-8-encoded.";
-        throw new ArgumentException (msg, "message");
-      }
-
-      if (bytes.Length > 125) {
-        var msg = "Its size is greater than 125 bytes.";
-        throw new ArgumentOutOfRangeException ("message", msg);
-      }
-
-      var frame = WebSocketFrame.CreatePingFrame (bytes, false);
-      return Broadping (frame.ToArray (), _waitTime);
-    }
-
     /// <summary>
     /// Closes the specified session.
     /// </summary>