diff --git a/includes/theme.inc b/includes/theme.inc
index e7fec486d5a619d1b5e4fa0be4cbb092574808b0..c5516192a36815a8851dbfc3162d63edb8adb9f0 100644
--- a/includes/theme.inc
+++ b/includes/theme.inc
@@ -382,6 +382,8 @@ function _theme_build_registry($theme, $base_theme, $theme_engine) {
   // Finally, hooks provided by the theme itself.
   _theme_process_registry($cache, $theme->name, 'theme', $theme->name, dirname($theme->filename));
 
+  // Let modules alter the registry
+  drupal_alter('theme_registry', $cache);
   return $cache;
 }