diff --git a/templates/service-worker.js b/templates/service-worker.js
index 2e31faf..0a12a27 100644
--- a/templates/service-worker.js
+++ b/templates/service-worker.js
@@ -3,9 +3,10 @@ const ASSETS = `cache${timestamp}`
 
 // `shell` is an array of all the files generated by webpack,
 // `assets` is an array of everything in the `assets` directory
-const toCache = __shell__.concat(__assets__)
+const assets = __assets__.map(file => file.startsWith('/') ? file : `/${file}`)
+const toCache = __shell__.concat(assets)
   .filter(filename => !filename.endsWith('.map'))
-  .filter(filename => !filename.startsWith('apple-icon'))
+  .filter(filename => !filename.startsWith('/apple-icon'))
 const cached = new Set(toCache)
 
 // `routes` is an array of `{ pattern: RegExp }` objects that
@@ -48,7 +49,7 @@ self.addEventListener('fetch', event => {
 
   event.respondWith((async function () {
     // always serve assets and webpack-generated files from cache
-    if (cached.has(url.pathname)) {
+    if (url.origin === self.origin && cached.has(url.pathname)) {
       return caches.match(req)
     }