diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index b721cb0e..b027c3da 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -2692,17 +2692,18 @@ namespace WebSocketSharp
     /// the WebSocket connection.
     /// </summary>
     /// <returns>
-    /// <c>true</c> if the ping has been sent and then a pong has been
-    /// received within a time; otherwise, <c>false</c>.
+    /// <c>true</c> if the sending a ping has done with no error and
+    /// a pong has been received within a time; otherwise, <c>false</c>.
     /// </returns>
     /// <param name="message">
     /// A <see cref="string"/> that represents the message to send.
+    /// Its size must be 125 bytes or less in UTF-8.
     /// </param>
     /// <exception cref="ArgumentNullException">
     /// <paramref name="message"/> is <see langword="null"/>.
     /// </exception>
     /// <exception cref="ArgumentException">
-    /// <paramref name="message"/> could not be UTF8 encoded.
+    /// <paramref name="message"/> could not be UTF-8-encoded.
     /// </exception>
     /// <exception cref="ArgumentOutOfRangeException">
     /// The size of <paramref name="message"/> is greater than 125 bytes.