diff -u includes/bootstrap.inc includes/bootstrap.inc
--- includes/bootstrap.inc	7 Oct 2010 21:55:51 -0000
+++ includes/bootstrap.inc
@@ -1121,6 +1121,7 @@
       timer_start('page');
       // Initialize the configuration
       conf_init();
+      $GLOBALS['simpletest_installed'] = TRUE;
       break;
 
     case DRUPAL_BOOTSTRAP_EARLY_PAGE_CACHE:
@@ -1140,7 +1141,6 @@
       // The user agent header is used to pass a database prefix in the request when
       // running tests. However, for security reasons, it is imperative that we
       // validate we ourselves made the request.
-      $GLOBALS['simpletest_installed'] = TRUE;
       if (isset($_SERVER['HTTP_USER_AGENT']) && preg_match("/^(simpletest\d+);/", $_SERVER['HTTP_USER_AGENT'], $matches)) {
         if (!drupal_valid_test_ua($_SERVER['HTTP_USER_AGENT'])) {
           header($_SERVER['SERVER_PROTOCOL'] . ' 403 Forbidden');