diff --git a/modules/system/system.module b/modules/system/system.module
index 946ef0c..4cb594e 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -2496,6 +2496,11 @@ function _system_rebuild_theme_data() {
     $themes[$key]->filename = $theme->uri;
     $themes[$key]->info = drupal_parse_info_file($theme->uri) + $defaults;
 
+    // The info key is required (http://drupal.org/node/542202), but to avoid
+    // errors in the menu system we set a reasonable default if it is not
+    // provided.
+    $themes[$key]->info += array('name' => $key);
+
     // Invoke hook_system_info_alter() to give installed modules a chance to
     // modify the data in the .info files if necessary.
     $type = 'theme';