diff --git a/sites/default/default.settings.php b/sites/default/default.settings.php
index 562f998..e2f6ea2 100644
--- a/sites/default/default.settings.php
+++ b/sites/default/default.settings.php
@@ -565,3 +565,18 @@ $conf['404_fast_html'] = '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"
  * Remove the leading hash signs to disable.
  */
 # $conf['allow_authorize_operations'] = FALSE;
+
+/**
+ * Theme debugging:
+ *
+ * When debugging is enabled:
+ * - The markup of each template is surrounded by HTML comments that contain
+ *   theming information, such as template file name suggestions.
+ * - Note that this debugging markup will cause automated tests that directly
+ *   check rendered HTML to fail.
+ *
+ * Not recommended in production environments.
+ *
+ * Remove the leading hash sign to enable.
+ */
+# $conf['theme_debug'] = TRUE;
