diff --git a/websocket-sharp/Net/WebHeaderCollection.cs b/websocket-sharp/Net/WebHeaderCollection.cs
index 976a1bd9..62993a57 100644
--- a/websocket-sharp/Net/WebHeaderCollection.cs
+++ b/websocket-sharp/Net/WebHeaderCollection.cs
@@ -1229,13 +1229,13 @@ namespace WebSocketSharp.Net
     /// </param>
     /// <exception cref="ArgumentException">
     ///   <para>
-    ///   <paramref name="header"/> is a restricted header.
+    ///   <paramref name="value"/> contains an invalid character.
     ///   </para>
     ///   <para>
     ///   -or-
     ///   </para>
     ///   <para>
-    ///   <paramref name="value"/> contains an invalid character.
+    ///   <paramref name="header"/> is a restricted header.
     ///   </para>
     /// </exception>
     /// <exception cref="ArgumentOutOfRangeException">