diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index b4c2c53a34..c37beeeec3 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -631,6 +631,7 @@ function trackback($trackback_url, $title, $excerpt, $ID) {
 	$http_request .= 'Host: '.$trackback_url['host']."\r\n";
 	$http_request .= 'Content-Type: application/x-www-form-urlencoded; charset='.get_settings('blog_charset')."\r\n";
 	$http_request .= 'Content-Length: '.strlen($query_string)."\r\n";
+	$http_request .= "User-Agent: WordPress/" . get_settings('version');
 	$http_request .= "\r\n";
 	$http_request .= $query_string;
 	if ( '' == $trackback_url['port'] )