diff --git a/background/storage.js b/background/storage.js
index 0fe28c29..c0e1ce3a 100644
--- a/background/storage.js
+++ b/background/storage.js
@@ -542,10 +542,10 @@ function cleanupCachedFilters({force = false} = {}) {
 
 
 function getDomains(url) {
-  if (url.indexOf('file:') === 0) {
+  let d = /.*?:\/*([^/:]+)|$/.exec(url)[1];
+  if (!d || url.startsWith('file:')) {
     return [];
   }
-  let d = /.*?:\/*([^/:]+)/.exec(url)[1];
   const domains = [d];
   while (d.indexOf('.') !== -1) {
     d = d.substring(d.indexOf('.') + 1);