diff --git a/wp-trackback.php b/wp-trackback.php
index cd68f4cf0..5d942808b 100644
--- a/wp-trackback.php
+++ b/wp-trackback.php
@@ -41,7 +41,7 @@ $charset   = $_POST['charset'];
 if ($charset)
 	$charset = strtoupper( trim($charset) );
 else
-	$charset = 'auto';
+	$charset = 'ASCII, UTF-8, ISO-8859-1, JIS, EUC-JP, SJIS';
 
 if ( function_exists('mb_convert_encoding') ) { // For international trackbacks
 	$title     = mb_convert_encoding($title, get_settings('blog_charset'), $charset);