diff --git a/public/index.php b/public/index.php
index bafc8aa..2c11f2a 100644
--- a/public/index.php
+++ b/public/index.php
@@ -23,9 +23,9 @@ require_once __DIR__ . "/../lib/required_public.php";
 // Allow setting the page background to match the style of a parent frame
 if (isset($_GET["backgroundcolor"]) && !empty($_GET["backgroundcolor"]) && preg_match("/^[a-z0-9#\-]+$/i", $_GET["backgroundcolor"])) {
     ?>
-    <style>
+    <style nonce="<?php echo $SECURE_NONCE; ?>">
         html,body {
-            background-color: <?php echo $_GET["backgroundcolor"]; ?>
+            background-color: <?php echo $_GET["backgroundcolor"]; ?>;
         }
     </style>
     <?php