diff -u modules/system/system.module modules/system/system.module
--- modules/system/system.module	16 Dec 2010 05:33:25 -0000
+++ modules/system/system.module
@@ -833,7 +833,7 @@
       // Record the name of each theme found in the file system.
       $names[] = $theme->name;
       // Update the contents of the system table.
-      if (isset($theme->status) && MAINTENANCE_MODE != 'install') {
+      if (isset($theme->status) && (defined('MAINTENANCE_MODDE') && MAINTENANCE_MODE != 'install')) {
         db_query("UPDATE {system} SET owner = '%s', info = '%s', filename = '%s' WHERE name = '%s' AND type = '%s'", $theme->owner, serialize($theme->info), $theme->filename, $theme->name, 'theme');
       }
       else {