diff --git a/app/assets/javascripts/discourse/lib/utilities.js.es6 b/app/assets/javascripts/discourse/lib/utilities.js.es6
index 82e3cd94e..6dc7b93ec 100644
--- a/app/assets/javascripts/discourse/lib/utilities.js.es6
+++ b/app/assets/javascripts/discourse/lib/utilities.js.es6
@@ -226,7 +226,7 @@ export function authorizedExtensions() {
 export function uploadLocation(url) {
   if (Discourse.CDN) {
     url = Discourse.getURLWithCDN(url);
-    return url.startsWith('//') ? 'http:' + url : url;
+    return /^\/\//.test(url) ? 'http:' + url : url;
   } else if (Discourse.SiteSettings.enable_s3_uploads) {
     return 'https:' + url;
   } else {