diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index 9cd873d2..f39973c2 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -2858,29 +2858,74 @@ namespace WebSocketSharp
     }
 
     /// <summary>
-    /// Closes the WebSocket connection asynchronously with the specified
-    /// <paramref name="code"/> and <paramref name="reason"/>, and releases
-    /// all associated resources.
+    /// Closes the connection asynchronously with the specified
+    /// <paramref name="code"/> and <paramref name="reason"/>.
     /// </summary>
     /// <remarks>
     ///   <para>
-    ///   This method does nothing if the current state of the connection is
-    ///   Closing or Closed.
+    ///   This method does not wait for the close to be complete.
     ///   </para>
     ///   <para>
-    ///   This method does not wait for the close to be complete.
+    ///   And this method does nothing if the current state of
+    ///   the connection is Closing or Closed.
     ///   </para>
     /// </remarks>
     /// <param name="code">
-    /// A <see cref="ushort"/> that represents the status code indicating
-    /// the reason for the close. The status codes are defined in
-    /// <see href="http://tools.ietf.org/html/rfc6455#section-7.4">
-    /// Section 7.4</see> of RFC 6455.
+    ///   <para>
+    ///   A <see cref="ushort"/> that represents the status code
+    ///   indicating the reason for the close.
+    ///   </para>
+    ///   <para>
+    ///   The status codes are defined in
+    ///   <see href="http://tools.ietf.org/html/rfc6455#section-7.4">
+    ///   Section 7.4</see> of RFC 6455.
+    ///   </para>
     /// </param>
     /// <param name="reason">
-    /// A <see cref="string"/> that represents the reason for the close.
-    /// The size must be 123 bytes or less.
+    ///   <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="ArgumentOutOfRangeException">
+    ///   <para>
+    ///   <paramref name="code"/> is less than 1000 or greater than 4999.
+    ///   </para>
+    ///   <para>
+    ///   -or-
+    ///   </para>
+    ///   <para>
+    ///   The size of <paramref name="reason"/> is greater than 123 bytes.
+    ///   </para>
+    /// </exception>
+    /// <exception cref="ArgumentException">
+    ///   <para>
+    ///   <paramref name="code"/> is 1011 (server error).
+    ///   It cannot be used by clients.
+    ///   </para>
+    ///   <para>
+    ///   -or-
+    ///   </para>
+    ///   <para>
+    ///   <paramref name="code"/> is 1010 (mandatory extension).
+    ///   It cannot be used by servers.
+    ///   </para>
+    ///   <para>
+    ///   -or-
+    ///   </para>
+    ///   <para>
+    ///   <paramref name="code"/> is 1005 (no status) and
+    ///   there is <paramref name="reason"/>.
+    ///   </para>
+    ///   <para>
+    ///   -or-
+    ///   </para>
+    ///   <para>
+    ///   <paramref name="reason"/> could not be UTF-8-encoded.
+    ///   </para>
+    /// </exception>
     public void CloseAsync (ushort code, string reason)
     {
       if (!code.IsCloseStatusCode ()) {