Getting navigator.hardwareConcurrency throws on workers

[andreubotella]

// main.js
new Worker(new URL("./worker.js", import.meta.url).href, {type: "module"});

// worker.js
console.log(navigator.hardwareConcurrency);

error: Uncaught (in worker "") TypeError: Illegal invocation
console.log(navigator.hardwareConcurrency);
                      ^
    at Object.assertBranded (deno:ext/webidl/00_webidl.js:923:13)
    at WorkerNavigator.get [as hardwareConcurrency] (deno:runtime/js/99_main.js:351:16)
    at file:///home/abotella/worker-test/hardwareConcurrency/worker.js:1:23
error: Uncaught (in promise) Error: Unhandled error event in child worker.
    at Worker.#pollControl (deno:runtime/js/11_workers.js:267:21)