diff --git a/wp-includes/comment-functions.php b/wp-includes/comment-functions.php
index c5214793c3..630866956f 100644
--- a/wp-includes/comment-functions.php
+++ b/wp-includes/comment-functions.php
@@ -109,8 +109,6 @@ function wp_allow_comment($commentdata) {
 	global $wpdb;
 	extract($commentdata);
 
-	$comment_user_domain = apply_filters('pre_comment_user_domain', gethostbyaddr($comment_author_IP) );
-
 	// Simple duplicate check
 	$dupe = "SELECT comment_ID FROM $wpdb->comments WHERE comment_post_ID = '$comment_post_ID' AND ( comment_author = '$comment_author' ";
 	if ( $comment_author_email )