diff --git a/lib/utils/resolve-url.js b/lib/utils/resolve-url.js
index fa98841801..5dd89cbcf2 100644
--- a/lib/utils/resolve-url.js
+++ b/lib/utils/resolve-url.js
@@ -28,6 +28,9 @@ export function resolveUrl(url, baseURI) {
   if (url && ABS_URL.test(url)) {
     return url;
   }
+  if (url === '//') {
+    return url;
+  }
   // Lazy feature detection.
   if (workingURL === undefined) {
     workingURL = false;