--- includes/bootstrap.inc.1.306	2009-09-21 09:07:07.000000000 +0100
+++ includes/bootstrap.inc	2009-09-30 22:16:34.000000000 +0100
@@ -1438,7 +1438,7 @@ function drupal_get_bootstrap_phase() {
 
 function _drupal_bootstrap($phase) {
   global $conf, $user;
-  static $cache;
+  static $cache, $hook_boot_invoked = FALSE;
 
   switch ($phase) {
 
@@ -1469,15 +1469,16 @@ function _drupal_bootstrap($phase) {
         // Make sure there is a user object because it's timestamp will be
         // checked, hook_boot might check for anonymous user etc.
         $user = drupal_anonymous_user();
+        // If the skipping of the bootstrap hooks is not enforced, call
+        // hook_boot.
+        if (variable_get('page_cache_invoke_hooks', TRUE)) {
+          bootstrap_invoke_all('boot');
+          $hook_boot_invoked = TRUE;
+        }
         // Get the page from the cache.
         $cache = drupal_page_get_cache();
         // If there is a cached page, display it.
         if (is_object($cache)) {
-          // If the skipping of the bootstrap hooks is not enforced, call
-          // hook_boot.
-          if (variable_get('page_cache_invoke_hooks', TRUE)) {
-            bootstrap_invoke_all('boot');
-          }
           header('X-Drupal-Cache: HIT');
           drupal_serve_page_from_cache($cache);
           // If the skipping of the bootstrap hooks is not enforced, call
@@ -1521,7 +1522,9 @@ function _drupal_bootstrap($phase) {
       break;
 
     case DRUPAL_BOOTSTRAP_PAGE_HEADER:
-      bootstrap_invoke_all('boot');
+      if (!$hook_boot_invoked) {
+        bootstrap_invoke_all('boot');
+      }
       if (!$cache && drupal_page_is_cacheable()) {
         header('X-Drupal-Cache: MISS');
       }