diff --git a/package.json b/package.json
index 491eb9fe56..0a019919b3 100644
--- a/package.json
+++ b/package.json
@@ -41,7 +41,7 @@
         "build-stats": "yarn clean && yarn build:genfiles && yarn build:bundle-stats",
         "build:res": "node scripts/copy-res.ts",
         "build:genfiles": "yarn build:res && yarn build:module_system",
-        "build:modernizr": "modernizr -c .modernizr.json -d src/vector/modernizr.js",
+        "build:modernizr": "modernizr -c .modernizr.json -d src/vector/modernizr.js && mv src/vector/modernizr.js src/vector/modernizr.cjs",
         "build:bundle": "webpack --progress --mode production",
         "build:bundle-stats": "webpack --progress --mode production --json > webpack-stats.json",
         "build:module_system": "node module_system/scripts/install.ts",
diff --git a/src/vector/index.ts b/src/vector/index.ts
index 3dfcbe6cdf..2010c95d75 100644
--- a/src/vector/index.ts
+++ b/src/vector/index.ts
@@ -15,7 +15,7 @@ import { shouldPolyfill as shouldPolyFillIntlSegmenter } from "@formatjs/intl-se
 
 // These are things that can run before the skin loads - be careful not to reference the react-sdk though.
 import { parseQsFromFragment } from "./url_utils";
-import "./modernizr";
+import "./modernizr.cjs";
 
 // Import shared components CSS
 import "@element-hq/web-shared-components/dist/element-web-shared-components.css";
diff --git a/src/vector/modernizr.js b/src/vector/modernizr.cjs
similarity index 99%
rename from src/vector/modernizr.js
rename to src/vector/modernizr.cjs
index 932513ebe8..87c3bca20e 100644
--- a/src/vector/modernizr.js
+++ b/src/vector/modernizr.cjs
@@ -1,5 +1,5 @@
 /*!
- * modernizr v3.13.0
+ * modernizr v3.13.1
  * Build https://modernizr.com/download?-cors-cryptography-cssanimations-cssfilters-displaytable-es5date-es5function-es5object-es5undefined-es6array-es6collections-es6string-fetch-flexbox-json-localstorage-objectfit-promises-resizeobserver-sandbox-svg-svgasimg-svgfilters-urlparser-urlsearchparams-webaudio-dontmin
  *
  * Copyright (c)
@@ -35,7 +35,7 @@
    * @access public
    */
   var ModernizrProto = {
-    _version: '3.13.0',
+    _version: '3.13.1',
 
     // Any settings that don't work as separate modules
     // can go in here as configuration.