diff --git a/SeedDMS_Core/Core/inc.ClassDocument.php b/SeedDMS_Core/Core/inc.ClassDocument.php
index 96d982680..d883d33d6 100644
--- a/SeedDMS_Core/Core/inc.ClassDocument.php
+++ b/SeedDMS_Core/Core/inc.ClassDocument.php
@@ -220,6 +220,27 @@ class SeedDMS_Core_Document extends SeedDMS_Core_Object { /* {{{ */
 		$this->_notifyList = array();
 		$this->_latestContent = null;
 		$this->_content = null;
+        /* Cache */
+        $this->clearCache();
+	} /* }}} */
+
+	/**
+     * Clear cache of this instance.
+     *
+     * The result of some expensive database actions (e.g. get all subfolders
+     * or documents) will be saved in a class variable to speed up consecutive
+     * calls of the same method. If a second call of the same method shall not
+     * use the cache, then it must be cleared.
+     *
+	 */
+	public function clearCache() { /* {{{ */
+        $this->_parent = null;
+        $this->_owner = null;
+        $this->_documentLinks = null;
+        $this->_documentFiles = null;
+        $this->_content = null;
+        $this->_accessList = null;
+        $this->_notifyList = null;
 	} /* }}} */
 
 	/**