Index: modules/system/system.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.install,v
retrieving revision 1.472
diff -u -p -r1.472 system.install
--- modules/system/system.install	8 Jun 2010 05:44:07 -0000	1.472
+++ modules/system/system.install	13 Jun 2010 13:28:40 -0000
@@ -269,8 +269,18 @@ function system_requirements($phase) {
     // By default no private files directory is configured. For private files
     // to be secure the admin needs to provide a path outside the webroot.
     variable_get('file_private_path', FALSE),
-    variable_get('file_temporary_path', sys_get_temp_dir()),
   );
+
+  // We don't check for the temporary files directory at install time
+  // unless it has been set in settings.php, because if it fails here,
+  // the user has no alternative but to fix the suggested directory.
+  if ($phase == 'install') {
+    $directories[] = variable_get('file_temporary_path', FALSE);
+  }
+  else {
+    $directories[] = variable_get('file_temporary_path', file_directory_temp());
+  }
+
   $requirements['file system'] = array(
     'title' => $t('File system'),
   );