diff --git a/app/javascript/flavours/glitch/service_worker/caching.ts b/app/javascript/flavours/glitch/service_worker/caching.ts
index 96c2898dd7..304f0284d6 100644
--- a/app/javascript/flavours/glitch/service_worker/caching.ts
+++ b/app/javascript/flavours/glitch/service_worker/caching.ts
@@ -18,6 +18,10 @@ export async function cacheRoot() {
 export function handleFetch(event: FetchEvent) {
   const url = new URL(event.request.url);
 
+  if (url.protocol !== 'http:' && url.protocol !== 'https:') {
+    return;
+  }
+
   if (url.pathname === '/auth/sign_out') {
     event.respondWith(handleLogout(event));
   } else if (/intl\/.*\.js$/.test(url.pathname)) {