diff --git a/phpBB/includes/functions_user.php b/phpBB/includes/functions_user.php
index 2be9d089a5..71c4f41817 100644
--- a/phpBB/includes/functions_user.php
+++ b/phpBB/includes/functions_user.php
@@ -26,8 +26,8 @@ if (!defined('IN_PHPBB'))
 * @param array &$user_id_ary The user ids to check or empty if usernames used
 * @param array &$username_ary The usernames to check or empty if user ids used
 * @param mixed $user_type Array of user types to check, false if not restricting by user type
-* @param bool $update_references If false, the supplied array is unset and appears unchanged from where it was called
-* @return null
+* @param boolean $update_references If false, the supplied array is unset and appears unchanged from where it was called
+* @return boolean|string Returns false on success, error string on failure
 */
 function user_get_id_name(&$user_id_ary, &$username_ary, $user_type = false, $update_references = false)
 {