diff --git a/core/model/Hierarchy.php b/core/model/Hierarchy.php
index 44a5a999b..d067c98f8 100644
--- a/core/model/Hierarchy.php
+++ b/core/model/Hierarchy.php
@@ -633,6 +633,9 @@ class Hierarchy extends DataObjectDecorator {
 		$this->_cache_children = null;
 		$this->_cache_allChildrenIncludingDeleted = null;
 		$this->_cache_allChildren = null;
+		self::$marked = array();
+		self::$expanded = array();
+		self::$treeOpened = array();
 	}
 
 }