diff --git a/app/capabilities.js b/app/capabilities.js
index 5b746bdc..76a2d8c1 100644
--- a/app/capabilities.js
+++ b/app/capabilities.js
@@ -75,6 +75,7 @@ async function polyfillStreams() {
 }
 
 export default async function capabilities() {
+  const serviceWorker = 'serviceWorker' in navigator;
   let crypto = await checkCrypto();
   const nativeStreams = checkStreams();
   let polyStreams = false;
@@ -91,11 +92,10 @@ export default async function capabilities() {
   return {
     account,
     crypto,
+    serviceWorker,
     streamUpload: nativeStreams || polyStreams,
     streamDownload:
-      nativeStreams &&
-      'serviceWorker' in navigator &&
-      browserName() !== 'safari',
+      nativeStreams && serviceWorker && browserName() !== 'safari',
     multifile: nativeStreams || polyStreams
   };
 }
diff --git a/app/main.js b/app/main.js
index c6afa043..3f11594a 100644
--- a/app/main.js
+++ b/app/main.js
@@ -28,8 +28,9 @@ if (process.env.NODE_ENV === 'production') {
 (async function start() {
   const app = routes(choo());
   const capa = await capabilities();
-  if (capa.streamDownload) {
-    navigator.serviceWorker.register('/serviceWorker.js');
+  if (capa.serviceWorker) {
+    await navigator.serviceWorker.register('/serviceWorker.js');
+    await navigator.serviceWorker.ready;
   }
 
   const translate = await getTranslator(LOCALE);