diff --git a/addressbook/inc/hook_config_validate.inc.php b/addressbook/inc/hook_config_validate.inc.php
new file mode 100644
index 0000000000..30d80be57f
--- /dev/null
+++ b/addressbook/inc/hook_config_validate.inc.php
@@ -0,0 +1,54 @@
+<?php
+  /**************************************************************************\
+  * phpGroupWare                                                             *
+  * http://www.phpgroupware.org                                              *
+  * Written by Mark Peters <skeeter@phpgroupware.org>                        *
+  * --------------------------------------------                             *
+  *  This program is free software; you can redistribute it and/or modify it *
+  *  under the terms of the GNU General Public License as published by the   *
+  *  Free Software Foundation; either version 2 of the License, or (at your  *
+  *  option) any later version.                                              *
+  \**************************************************************************/
+
+  /* $Id$ */
+
+	/*
+	  Set a global flag to indicate this file was found by admin/config.php.
+	  config.php will unset it after parsing the form values.
+	*/
+	$GLOBALS['phpgw_info']['server']['found_validation_hook'] = True;
+
+	/* Check a specific setting.  Name must match the setting. */
+	function ldap_contact_context($value='')
+	{
+		if($value == $GLOBALS['phpgw_info']['server']['ldap_context'])
+		{
+			$GLOBALS['config_error'] = 'Contact context for ldap must be different from the context used for accounts';
+		}
+		elseif($value == $GLOBALS['phpgw_info']['server']['ldap_group_context'])
+		{
+			$GLOBALS['config_error'] = 'Contact context for ldap must be different from the context used for groups';
+		}
+		else
+		{
+			$GLOBALS['config_error'] = '';
+		}
+	}
+
+	/* Check all settings to validate input.  Name must be 'final_validation' */
+	function final_validation($value='')
+	{
+		if($value['contact_repository'] == 'ldap' && !$value['ldap_contact_dn'])
+		{
+			$GLOBALS['config_error'] = 'Contact dn must be set';
+		}
+		elseif($value['contact_repository'] == 'ldap' && !$value['ldap_contact_context'])
+		{
+			$GLOBALS['config_error'] = 'Contact context must be set';
+		}
+		else
+		{
+			$GLOBALS['config_error'] = '';
+		}
+	}
+?>