WeakMap crash with preload

main.js

import { MyClass } from './myclass';

const weak = new WeakMap();
weak.set(MyClass, {});
trace('Success\n');

manifest.json

{
	"include": [
		"$(MODDABLE)/examples/manifest_base.json"
	],
	"modules": {
		"*": ["./*"]
	},
	"preload": ["myclass"],
	"strip": []
}

myclass.js

export class MyClass {}