diff --git a/SeedDMS_Core/Core/inc.ClassDMS.php b/SeedDMS_Core/Core/inc.ClassDMS.php
index 070d9f098..f9009b4bf 100644
--- a/SeedDMS_Core/Core/inc.ClassDMS.php
+++ b/SeedDMS_Core/Core/inc.ClassDMS.php
@@ -188,10 +188,22 @@ class SeedDMS_Core_DMS {
 	 */
 	public $callbacks;
 
+	/**
+	 * @var string last error message. This can be set by hooks to pass an
+	 * error message from the hook to the application which has called the
+	 * method containing the hook. For example SeedDMS_Core_Document::remove()
+	 * calls the hook 'onPreRemoveDocument'. The hook function can set $dms->lasterror
+	 * which can than be read when SeedDMS_Core_Document::remove() fails.
+	 * This variable could be set in any SeedDMS_Core class, but is currently
+	 * only set by hooks.
+	 * @access public
+	 */
+	public $lasterror;
+
 	/**
 	 * @var SeedDMS_Core_DMS
 	 */
-	public $_dms;
+//	public $_dms;
 
 
 	/**
@@ -381,6 +393,7 @@ class SeedDMS_Core_DMS {
 		$this->classnames['user'] = 'SeedDMS_Core_User';
 		$this->classnames['group'] = 'SeedDMS_Core_Group';
 		$this->callbacks = array();
+		$this->lasterror = '';
 		$this->version = '@package_version@';
 		if($this->version[0] == '@')
 			$this->version = '5.1.16';
@@ -2033,8 +2046,8 @@ class SeedDMS_Core_DMS {
 		$user = $this->getUser($this->db->getInsertID('tblUsers'));
 
 		/* Check if 'onPostAddUser' callback is set */
-		if(isset($this->_dms->callbacks['onPostAddUser'])) {
-			foreach($this->_dms->callbacks['onPostUser'] as $callback) {
+		if(isset($this->callbacks['onPostAddUser'])) {
+			foreach($this->callbacks['onPostUser'] as $callback) {
 				/** @noinspection PhpStatementHasEmptyBodyInspection */
 				if(!call_user_func($callback[0], $callback[1], $user)) {
 				}
@@ -2096,8 +2109,8 @@ class SeedDMS_Core_DMS {
 		$group = $this->getGroup($this->db->getInsertID('tblGroups'));
 
 		/* Check if 'onPostAddGroup' callback is set */
-		if(isset($this->_dms->callbacks['onPostAddGroup'])) {
-			foreach($this->_dms->callbacks['onPostAddGroup'] as $callback) {
+		if(isset($this->callbacks['onPostAddGroup'])) {
+			foreach($this->callbacks['onPostAddGroup'] as $callback) {
 				/** @noinspection PhpStatementHasEmptyBodyInspection */
 				if(!call_user_func($callback[0], $callback[1], $group)) {
 				}
@@ -2188,8 +2201,8 @@ class SeedDMS_Core_DMS {
 		$category = $this->getKeywordCategory($this->db->getInsertID('tblKeywordCategories'));
 
 		/* Check if 'onPostAddKeywordCategory' callback is set */
-		if(isset($this->_dms->callbacks['onPostAddKeywordCategory'])) {
-			foreach($this->_dms->callbacks['onPostAddKeywordCategory'] as $callback) {
+		if(isset($this->callbacks['onPostAddKeywordCategory'])) {
+			foreach($this->callbacks['onPostAddKeywordCategory'] as $callback) {
 				/** @noinspection PhpStatementHasEmptyBodyInspection */
 				if(!call_user_func($callback[0], $callback[1], $category)) {
 				}
@@ -2265,8 +2278,8 @@ class SeedDMS_Core_DMS {
 		$category = $this->getDocumentCategory($this->db->getInsertID('tblCategory'));
 
 		/* Check if 'onPostAddDocumentCategory' callback is set */
-		if(isset($this->_dms->callbacks['onPostAddDocumentCategory'])) {
-			foreach($this->_dms->callbacks['onPostAddDocumentCategory'] as $callback) {
+		if(isset($this->callbacks['onPostAddDocumentCategory'])) {
+			foreach($this->callbacks['onPostAddDocumentCategory'] as $callback) {
 				/** @noinspection PhpStatementHasEmptyBodyInspection */
 				if(!call_user_func($callback[0], $callback[1], $category)) {
 				}