diff --git a/subpathauto.module b/subpathauto.module
index 4fd2eda..0b71cd5 100644
--- a/subpathauto.module
+++ b/subpathauto.module
@@ -20,6 +20,12 @@ function subpathauto_menu() {
  * Implements hook_url_inbound_alter().
  */
 function subpathauto_url_inbound_alter(&$path, $original_path, $language) {
+  if (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update') {
+    global $theme;
+    if (!isset($theme)) {
+      menu_set_custom_theme();
+    }
+  }
   // If the current menu item exists at this path, then we should not continue
   // processing.
   $item = menu_get_item($path);