Index: t3lib/config_default.php
===================================================================
--- t3lib/config_default.php	(revision 8083)
+++ t3lib/config_default.php	(working copy)
@@ -558,15 +558,16 @@
 define('TYPO3_REQUESTTYPE_BE', 2);
 define('TYPO3_REQUESTTYPE_CLI', 4);
 define('TYPO3_REQUESTTYPE_AJAX', 8);
+define('TYPO3_REQUESTTYPE_INSTALL', 16);
 define('TYPO3_REQUESTTYPE',
 	(TYPO3_MODE == 'FE' ? TYPO3_REQUESTTYPE_FE : 0) |
 	(TYPO3_MODE == 'BE' ? TYPO3_REQUESTTYPE_BE : 0) |
 	((defined('TYPO3_cliMode') && TYPO3_cliMode) ? TYPO3_REQUESTTYPE_CLI : 0) |
+	((defined('TYPO3_enterInstallScript') && TYPO3_enterInstallScript) ? TYPO3_REQUESTTYPE_INSTALL : 0) |
 	($TYPO3_AJAX ? TYPO3_REQUESTTYPE_AJAX : 0)
 );
 
 
-
 // *********************
 // Autoloader
 // *********************
Index: typo3/init.php
===================================================================
--- typo3/init.php	(revision 8084)
+++ typo3/init.php	(working copy)
@@ -339,7 +339,7 @@
 // ********************************************
 // Check if the install script should be run:
 // ********************************************
-if (defined('TYPO3_enterInstallScript') && TYPO3_enterInstallScript)	{
+if (TYPO3_REQUESTTYPE & TYPO3_REQUESTTYPE_INSTALL) {
 	if(!t3lib_extMgm::isLoaded('install')) {
 		die('Install Tool is not loaded as an extension.<br />You must add the key "install" to the list of installed extensions in typo3conf/localconf.php, $TYPO3_CONF_VARS[\'EXT\'][\'extList\'].');
 	}