Failed to execute 'open' on 'CacheStorage': Only cache name 'default' can be opened

The documentation says that caches.open(key) is supported, however trying to do so throws an error: Failed to execute 'open' on 'CacheStorage': Only cache name 'default' can be opened. I attempted several variation of keys, including the one provided in the docs caches.open('custom:cache')

Support is mentioned in two places:

https://developers.cloudflare.com/workers/learning/how-the-cache-works#cache-api

  • New namespaces – You can access a namespaced cache (separate from the cache shared with fetch requests) using let cache = await caches.open(CACHE_NAME) . This can be useful when writing new content to the cache, for example after running a more compute heavy operation such as parsing HTML or running a computation, to store them locally in the colo and readily access them on the following request, rather having to rerun the same operation. Note that caches.open Open external link is an async function, unlike caches.default .

https://developers.cloudflare.com/workers/runtime-apis/cache#accessing-cache

You may create and manage additional Cache instances via the caches.open Open external link method.

let myCache = await caches.open('custom:cache');
await myCache.match(request);