diff --git a/src/pages/api/config/[path].js b/src/pages/api/config/[path].js
index b7ac1f0c..a7da7eec 100644
--- a/src/pages/api/config/[path].js
+++ b/src/pages/api/config/[path].js
@@ -17,6 +17,7 @@ export default async function handler(req, res) {
   if (!['custom.css', 'custom.js'].includes(relativePath))
   {
     res.status(422).end('Unsupported file')
+    return // do not continue in the function
   }
 
   const filePath = path.join(CONF_DIR, relativePath);
diff --git a/src/pages/index.jsx b/src/pages/index.jsx
index 187f4c19..65426862 100644
--- a/src/pages/index.jsx
+++ b/src/pages/index.jsx
@@ -313,14 +313,16 @@ function Home({ initialSettings }) {
         <meta name="theme-color" content={themes[settings.color || "slate"][settings.theme || "dark"]} />
       </Head>
 
-      <style alt="custom">
+      <link rel="preload" href="/api/config/custom.css" as="fetch" crossorigin="anonymous" />
+      <style data-name="custom.css">
         <FileContent path="custom.css"
           loadingValue="/* Loading custom CSS... */"
           errorValue="/* Failed to load custom CSS... */"
           emptyValue="/* No custom CSS */"
         />
       </style>
-      <script alt="custom">
+      <link rel="preload" href="/api/config/custom.js" as="fetch" crossorigin="anonymous" />
+      <script data-name="custom.js">
         <FileContent path="custom.js"
           loadingValue="/* Loading custom JS... */"
           errorValue="/* Failed to load custom JS... */"