Rollup CommonJS bug

rollup.config.js

import commonjs from 'rollup-plugin-commonjs';

export default {
    entry: 'test.js',
    format: 'iife',
    moduleName: 'main',
    plugins: [
        commonjs({
            include: 'x.js'
        })
    ]
};

test.js

import x from './x';

console.log(x);

x.js

var x = {};

module.exports = x;
module.exports.default = x;