Broken module binding with top level await & dynamic import

a.js

import B from "./b.js";
console.log(B); // "undefined" or "X" depending on export in b.js

b.js

let x;
// export default x; // broken
export { x as default }; // ok
x = await import("./c.js").then((mod) => mod.default);

c.js

export default 'X';