diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index caf1529536..544427fca3 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1012,7 +1012,7 @@ function wp_check_filetype($filename, $mimes = null) {
 
 function wp_proxy_check($ipnum) {
 	if ( get_option('open_proxy_check') && isset($ipnum) ) {
-		$ipnum = preg_replace( '/([0-9]{1,3})\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}).*/', '$1', $ipnum );
+		$ipnum = preg_replace( '/([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}).*/', '$1', $ipnum );
 		$rev_ip = implode( '.', array_reverse( explode( '.', $ipnum ) ) );
 		$lookup = $rev_ip . '.sbl-xbl.spamhaus.org.';
 		if ( $lookup != gethostbyname( $lookup ) )