diff --git a/core/includes/install.inc b/core/includes/install.inc
index 99cfcf6..aa73e62 100644
--- a/core/includes/install.inc
+++ b/core/includes/install.inc
@@ -448,6 +448,10 @@ function drupal_install_system() {
   module_list_reset();
   module_implements_reset();
 
+  // @todo PHP 5.3.9 changes the behavior of is_subclass_of() with respect to
+  //   autoloaders. To allow earlier versions to properly find system.module,
+  //   warm the module list cache.
+  module_list();
   config_install_default_config('module', 'system');
 
   module_invoke('system', 'install');