diff --git a/.github/workflows/404.html b/.github/workflows/404.html
index 116ddbb7f8ad827..4c3a717c8aa2b0d 100644
--- a/.github/workflows/404.html
+++ b/.github/workflows/404.html
@@ -2,16 +2,9 @@
 <html>
   <head>
     <title>404 Page Not Found</title>
+    <script src="./404.js"></script>
   </head>
   <body>
     <h1>404 Page Not Found</h1>
-    <script>
-      if (document.location.hostname.endsWith("content.dev.mdn.mozit.cloud")) {
-        const link = document.createElement("a");
-        link.href = `https://developer.mozilla.org${location.pathname}`;
-        link.textContent = "View on MDN production server";
-        document.body.appendChild(link);
-      }
-    </script>
   </body>
 </html>
diff --git a/.github/workflows/404.js b/.github/workflows/404.js
new file mode 100644
index 000000000000000..b973f7202270e41
--- /dev/null
+++ b/.github/workflows/404.js
@@ -0,0 +1,8 @@
+window.addEventListener("DOMContentLoaded", () => {
+  if (document.location.hostname.endsWith("content.dev.mdn.mozit.cloud")) {
+    const link = document.createElement("a");
+    link.href = `https://developer.mozilla.org${location.pathname}`;
+    link.textContent = "View on MDN production server";
+    document.body.appendChild(link);
+  }
+});
diff --git a/.github/workflows/pr-test.yml b/.github/workflows/pr-test.yml
index cf61e3a63ebcada..e592b120cac026f 100644
--- a/.github/workflows/pr-test.yml
+++ b/.github/workflows/pr-test.yml
@@ -108,6 +108,7 @@ jobs:
           # Add the custom 404 page to provide production links to the unbuilt documents
           mkdir -p ${BUILD_OUT_ROOT}/en-us/_spas/
           cp -v ./.github/workflows/404.html ${BUILD_OUT_ROOT}/en-us/_spas/404.html
+          cp -v ./.github/workflows/404.js ${BUILD_OUT_ROOT}/en-us/_spas/404.js
 
           # Download the raw diff blob and store that inside the build
           # directory.
