Index: typo3/sysext/install/mod/class.tx_install.php
===================================================================
--- typo3/sysext/install/mod/class.tx_install.php	(revision 6058)
+++ typo3/sysext/install/mod/class.tx_install.php	(working copy)
@@ -308,7 +308,7 @@
 			$this->passwordOK=1;
 
 			$enableInstallToolFile = PATH_typo3conf . 'ENABLE_INSTALL_TOOL';
-			if (is_file ($enableInstallToolFile)) {
+			if (is_writable($enableInstallTool)) {
 					// Extend the age of the ENABLE_INSTALL_TOOL file by one hour
 				touch ($enableInstallToolFile);
 			}