Exported PropTypes shapes get lost in translation

Reproduce el comando de microbundle informado con la importación compartida de LocaleShape e inspecciona el bundle generado, donde la shape de PropTypes exportada se convierte en null. Compáralo con la compilación funcional que duplica la shape; se considera hecho cuando las shapes importadas siguen siendo válidas y la advertencia de prop-type de React ya no informa expected one of [null,null].

Hi there,
Thank you for the great work you've done with microbundle. For the record, here is how I'm using the lib:
microbundle --jsx React.createElement --no-compress --format modern,cjs

I'm using react in version 17 and microbundle in version 0.12.0-next.9

I've got a PropType shape that is used in several definitions:

import PropTypes from "prop-types";

 const LocaleShape = PropTypes.shape({
    // two-char language code ("en", "fr", "de")
    tag: PropTypes.string.isRequired,
    // human readable language description
    language: PropTypes.oneOf([PropTypes.object, PropTypes.string]).isRequired,
    //latin, cyrillic, etc.
    script: PropTypes.string,
    // two-char region code ("US", "CA", "GB", "CH")
    region: PropTypes.string,
    // text direction / orientation: right to left, left to right
    orientation: PropTypes.oneOf(["rtl", "ltr"]),
    // optional emoji string for displaying a flag 🇨🇬 🇲🇼 🇹🇩
    flag: PropTypes.string,
    // String that can be used to search for a locale
    keywords: PropTypes.string,
    // locale identifier of the fallback locale
    fallback: PropTypes.string,
    // optional identifier. If not specified, locale identifier will result in the concatenation
    // of tag and region, with a dash separator: "en-GB", "fr-CA", "nl-BE"
    id: PropTypes.string,
});
export default LocaleShape;

This shape is imported in different files:

LocaleChooser.propTypes = {
  value: PropTypes.oneOfType([LocaleShape, PropTypes.arrayOf(LocaleShape)]),
  locales: PropTypes.arrayOf(LocaleShape),
}

When the bundle is built, it looks like the exported PropType shape is turned into null, as explain the warnings I receive in console:

Warning: Failed prop type: Invalid prop `locales[0].language` of value `[object Object]` supplied to `LocaleChooser`, expected one of [null,null].

This warning is suppressed once I remove the imports and duplicate the LocaleShape in every file that requires it. Am I missing a parameter in the command?

Thanks for your help