Fails when a depedency (module) requires a webpack "external" module

Awesome library! I've just found an edge case when workerizing a module that depends on a webpack external.

In my webpack config i have:

module.exports = {
  // ...
  externals: {
    'config': JSON.stringify(config),
  },
  // ...
}

and in my worker module I have:

import * as config from 'config';

I'm using typescript in case that matters.

Here's the compilation error from webpack:

Module not found: Error: Can't resolve 'config' in '/directory/src'
 @ ./src/MyWorker.ts 1:0-33