diff --git a/site/public/sw.js b/site/public/sw.js
index caf9a3a..fa5ecde 100644
--- a/site/public/sw.js
+++ b/site/public/sw.js
@@ -5,7 +5,7 @@
 */
 
 // Bump this value on deploy to invalidate caches.
-const CACHE_VERSION = "v3";
+const CACHE_VERSION = "v4";
 
 const CACHE_SHELL = `shell-${CACHE_VERSION}`;
 const CACHE_PAGES = `pages-${CACHE_VERSION}`;
@@ -13,6 +13,9 @@ const CACHE_MEDIA = `media-${CACHE_VERSION}`;
 
 const SHELL_ASSETS = ["/", "/styles/global.css", "/favicon.png", "/robots.txt"];
 
+// Cache.addAll() throws if there are any duplicate requests.
+const SHELL_ASSETS_UNIQUE = Array.from(new Set(SHELL_ASSETS));
+
 // Keep media cache bounded so we don't grow indefinitely.
 const MAX_MEDIA_ENTRIES = 80;
 
@@ -58,7 +61,7 @@ self.addEventListener("install", (event) => {
   event.waitUntil(
     (async () => {
       const cache = await caches.open(CACHE_SHELL);
-      await cache.addAll(SHELL_ASSETS);
+      await cache.addAll(SHELL_ASSETS_UNIQUE);
       // Activate new worker ASAP to pick up new caching rules.
       await self.skipWaiting();
     })(),