Dynamically importing NPM modules errors

The following works fine in Node:

const parser = 'acorn';
const { parse } = await import(parser);

const parser = 'acorn';
const { parse } = await import(parser);

But with Deno gives the error:

Uncaught (in promise) TypeError: Loading unprepared module: npm:acorn@^8.9.0

Uncaught (in promise) TypeError: Loading unprepared module: npm:acorn@^8.9.0

Not sure what I should do to "prepare" it since I can't find any information on it?