diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 55ab90ccd1..a38c25311d 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -786,6 +786,7 @@ function trackback($trackback_url, $title, $excerpt, $ID) {
 */
 	@fclose($fs);
 
+	$tb_url = addslashes( $tb_url );
 	$wpdb->query("UPDATE $wpdb->posts SET pinged = CONCAT(pinged, '\n', '$tb_url') WHERE ID = '$ID'");
 	$wpdb->query("UPDATE $wpdb->posts SET to_ping = REPLACE(to_ping, '$tb_url', '') WHERE ID = '$ID'");
 	return $result;