Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.464
diff -u -p -r1.464 bootstrap.inc
--- includes/bootstrap.inc	13 Jan 2011 01:04:13 -0000	1.464
+++ includes/bootstrap.inc	19 Jan 2011 18:34:21 -0000
@@ -881,7 +881,7 @@ function drupal_page_is_cacheable($allow
   }
 
   return $allow_caching_static && ($_SERVER['REQUEST_METHOD'] == 'GET' || $_SERVER['REQUEST_METHOD'] == 'HEAD')
-    && !drupal_is_cli();
+    && !drupal_is_cli() && !variable_get('maintenance_mode', 0);
 }
 
 /**