diff --git a/phpBB/includes/session.php b/phpBB/includes/session.php
index e157053e61..2ee9365631 100644
--- a/phpBB/includes/session.php
+++ b/phpBB/includes/session.php
@@ -285,6 +285,17 @@ class session
 				break;
 			}
 
+			// Quick check for IPv4-mapped address in IPv6
+			if (stripos($ip, '::ffff:') === 0)
+			{
+				$ipv4 = substr($ip, 7);
+
+				if (preg_match(get_preg_expression('ipv4'), $ipv4))
+				{
+					$ip = $ipv4;
+				}
+			}
+
 			// Use the last in chain
 			$this->ip = $ip;
 		}
diff --git a/phpBB/install/database_update.php b/phpBB/install/database_update.php
index 83bbbf4577..4524dd20bf 100644
--- a/phpBB/install/database_update.php
+++ b/phpBB/install/database_update.php
@@ -119,6 +119,7 @@ $db->sql_connect($dbhost, $dbuser, $dbpasswd, $dbname, $dbport, false, false);
 unset($dbpasswd);
 
 $user->ip = (!empty($_SERVER['REMOTE_ADDR'])) ? htmlspecialchars($_SERVER['REMOTE_ADDR']) : '';
+$user->ip = (stripos($user->ip, '::ffff:') === 0) ? substr($user->ip, 7) : $user->ip;
 
 $sql = "SELECT config_value
 	FROM " . CONFIG_TABLE . "
diff --git a/phpBB/install/install_install.php b/phpBB/install/install_install.php
index 4c22db07b2..2800c26609 100644
--- a/phpBB/install/install_install.php
+++ b/phpBB/install/install_install.php
@@ -1236,6 +1236,7 @@ class install_install extends module
 		$current_time = time();
 
 		$user_ip = (!empty($_SERVER['REMOTE_ADDR'])) ? htmlspecialchars($_SERVER['REMOTE_ADDR']) : '';
+		$user_ip = (stripos($user_ip, '::ffff:') === 0) ? substr($user_ip, 7) : $user_ip;
 
 		if ($data['script_path'] !== '/')
 		{