Standard module bundler fails for `export default class {}`

[bakkot]

The program

export default class {}

with default options and using StandardModuleBundler generates a "program" containing

(function(global) {
  // ...
  require.define('1', function(module, exports, __dirname, __filename) {
    class {}
    exports['default'] = *default*;
  });
  return require('1');
}.call(this, this));

Note the class declaration without a name, and non-expression following exports['default'] =.