diff --git a/inc/bans.php b/inc/bans.php
index 81e38006..e629ddae 100644
--- a/inc/bans.php
+++ b/inc/bans.php
@@ -1,8 +1,8 @@
 <?php
 
-require 'inc/lib/IP/Lifo/IP/IP.php';
-require 'inc/lib/IP/Lifo/IP/BC.php';
-require 'inc/lib/IP/Lifo/IP/CIDR.php';
+require_once 'inc/lib/IP/Lifo/IP/IP.php';
+require_once 'inc/lib/IP/Lifo/IP/BC.php';
+require_once 'inc/lib/IP/Lifo/IP/CIDR.php';
 
 use Lifo\IP\CIDR;
 
diff --git a/inc/functions.php b/inc/functions.php
index 44712b16..821cb03e 100644
--- a/inc/functions.php
+++ b/inc/functions.php
@@ -23,10 +23,13 @@ require_once 'inc/mod/auth.php';
 require_once 'inc/lock.php';
 require_once 'inc/queue.php';
 require_once 'inc/polyfill.php';
+require_once 'inc/lib/IP/Lifo/IP/IP.php';
 @include_once 'inc/lib/parsedown/Parsedown.php'; // fail silently, this isn't a critical piece of code
 
 require_once 'inc/anti-bot.php'; // DELETE ME THIS IS FOR print_err function only!
 
+use Lifo\IP\IP; // for expanding IPv6 address in DNSBL()
+
 if (!extension_loaded('gettext')) {
 	require_once 'inc/lib/gettext/gettext.inc';
 }
@@ -1753,9 +1756,6 @@ function buildJavascript() {
 function checkDNSBL() {
 	global $config;
 
-	if (isIPv6())
-		return; // No IPv6 support yet.
-
 	if (!isset($_SERVER['REMOTE_ADDR']))
 		return; // Fix your web server configuration
 
@@ -1765,7 +1765,11 @@ function checkDNSBL() {
 	if (in_array($_SERVER['REMOTE_ADDR'], $config['dnsbl_exceptions']))
 		return;
 
-	$ipaddr = ReverseIPOctets($_SERVER['REMOTE_ADDR']);
+	if (isIPv6()) {
+		$ipaddr = ReverseIPv6Octets($_SERVER['REMOTE_ADDR']);
+	} else {
+		$ipaddr = ReverseIPv4Octets($_SERVER['REMOTE_ADDR']);
+	}
 
 	foreach ($config['dnsbl'] as $blacklist) {
 		if (!is_array($blacklist))
@@ -1801,10 +1805,14 @@ function isIPv6() {
 	return strstr($_SERVER['REMOTE_ADDR'], ':') !== false;
 }
 
-function ReverseIPOctets($ip) {
+function ReverseIPv4Octets($ip) {
 	return implode('.', array_reverse(explode('.', $ip)));
 }
 
+function ReverseIPv6Octets($ip) {
+	return strrev(implode(".", str_split(str_replace(':', '', IP::inet_expand($ip)))));
+}
+
 function wordfilters(&$body) {
         global $config;