diff --git a/websocket-sharp/WebSocket.cs b/websocket-sharp/WebSocket.cs
index df409438..179db29f 100644
--- a/websocket-sharp/WebSocket.cs
+++ b/websocket-sharp/WebSocket.cs
@@ -3068,12 +3068,13 @@ namespace WebSocketSharp
     /// 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.
-    /// The size must be 125 bytes or less in UTF-8.
+    ///   <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="ArgumentNullException">
-    /// <paramref name="message"/> is <see langword="null"/>.
-    /// </exception>
     /// <exception cref="ArgumentException">
     /// <paramref name="message"/> could not be UTF-8-encoded.
     /// </exception>