diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 497403b1e5..588a717f0e 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -3669,6 +3669,30 @@ function obtain_users_online_string($online_users, $item_id = 0, $item = 'forum'
 			}
 		}
 	}
+
+	/**
+	* Modify online userlist data
+	*
+	* @event core.obtain_users_online_string_before_modify
+	* @var	array	online_users		Array with online users data
+	*									from obtain_users_online()
+	* @var	int		item_id				Restrict online users to item id
+	* @var	string	item				Restrict online users to a certain
+	*									session item, e.g. forum for
+	*									session_forum_id
+	* @var	array	rowset				Array with online users data
+	* @var	array	user_online_link	Array with online users items (usernames)
+	* @since 3.1.10-RC1
+	*/
+	$vars = array(
+		'online_users',
+		'item_id',
+		'item',
+		'rowset',
+		'user_online_link',
+	);
+	extract($phpbb_dispatcher->trigger_event('core.obtain_users_online_string_before_modify', compact($vars)));
+
 	$online_userlist = implode(', ', $user_online_link);
 
 	if (!$online_userlist)