diff --git a/phpBB/includes/nestedset/interface.php b/phpBB/includes/nestedset/interface.php
index 9948ccf019..9a8f9c4eea 100644
--- a/phpBB/includes/nestedset/interface.php
+++ b/phpBB/includes/nestedset/interface.php
@@ -85,6 +85,9 @@ interface phpbb_nestedset_interface
 	/**
 	* Moves all children of one item to another item
 	*
+	* If the new parent already has children, the new children are appended
+	* to the list.
+	*
 	* @param int	$current_parent_id	The current parent item
 	* @param int	$new_parent_id		The new parent item
 	* @return bool True if any items where moved