diff --git a/config/config.sample.php b/config/config.sample.php
index be6e9343ed7..070fa3e75b3 100644
--- a/config/config.sample.php
+++ b/config/config.sample.php
@@ -2460,6 +2460,14 @@ $CONFIG = [
  */
 'upgrade.cli-upgrade-link' => '',
 
+/**
+ * Additional line(s) (string or array of strings)
+ * that will be added to .user.ini on each update by the updater.
+ *
+ * Defaults to ``''`` (empty string)
+ */
+'user_ini_additional_lines' => '',
+
 /**
  * Customize the server logs documentation link for exception handling.
  */