diff --git a/lib/wrapper-end.js b/lib/wrapper-end.js
index a4a959c1..a94d6435 100644
--- a/lib/wrapper-end.js
+++ b/lib/wrapper-end.js
@@ -1,7 +1,12 @@
 }
 
 // auto-load Promise and URL polyfills if needed in the browser
-if (typeof Promise === 'undefined' || (typeof URL !== 'function' && typeof URLPolyfill !== 'function')) {
+try {
+  var hasURL = typeof URLPolyfill != 'undefined' || typeof URL != 'undefined' && new URL('test:///').protocol == 'test:';
+}
+catch(e) {}
+
+if (typeof Promise === 'undefined' || !hasURL) {
   // document.write
   if (typeof document !== 'undefined') {
     var scripts = document.getElementsByTagName('script');