diff --git a/build-scripts/bundle.cjs b/build-scripts/bundle.cjs
index c341909b19..e0503a7a73 100644
--- a/build-scripts/bundle.cjs
+++ b/build-scripts/bundle.cjs
@@ -3,6 +3,8 @@ const env = require("./env.cjs");
 const paths = require("./paths.cjs");
 const { dependencies } = require("../package.json");
 
+const BABEL_PLUGINS = path.join(__dirname, "babel-plugins");
+
 // GitHub base URL to use for production source maps
 // Nightly builds use the commit SHA, otherwise assumes there is a tag that matches the version
 module.exports.sourceMapURL = () => {
@@ -100,22 +102,12 @@ module.exports.babelOptions = ({ latestBuild, isProdBuild, isTestBuild }) => ({
   ],
   plugins: [
     [
-      path.resolve(
-        paths.polymer_dir,
-        "build-scripts/babel-plugins/inline-constants-plugin.cjs"
-      ),
+      path.join(BABEL_PLUGINS, "inline-constants-plugin.cjs"),
       {
         modules: ["@mdi/js"],
         ignoreModuleNotFound: true,
       },
     ],
-    [
-      path.resolve(
-        paths.polymer_dir,
-        "build-scripts/babel-plugins/custom-polyfill-plugin.js"
-      ),
-      { method: "usage-global" },
-    ],
     // Minify template literals for production
     isProdBuild && [
       "template-html-minifier",
@@ -153,6 +145,17 @@ module.exports.babelOptions = ({ latestBuild, isProdBuild, isTestBuild }) => ({
   ],
   sourceMaps: !isTestBuild,
   overrides: [
+    {
+      // Add plugin to inject various polyfills, excluding the polyfills
+      // themselves to prevent self- injection.
+      plugins: [
+        [
+          path.join(BABEL_PLUGINS, "custom-polyfill-plugin.js"),
+          { method: "usage-global" },
+        ],
+      ],
+      exclude: /\/node_modules\/(?:unfetch|proxy-polyfill)\//,
+    },
     {
       // Use unambiguous for dependencies so that require() is correctly injected into CommonJS files
       // Exclusions are needed in some cases where ES modules have no static imports or exports, such as polyfills