Object.assign is not compatible with node 0.12

I’m submitting a bug report
Webpack version:
2.1.0-beta25

Please tell us about your environment:
Linux – Node 0.12

Current behavior:
cannot compile anymore due to runtime error:

/node_modules/webpack/lib/NormalModuleFactory.js:217
            return callback(null, Object.assign({}, item, {
                                         ^
TypeError: undefined is not a function

Solution is to replace Object.assign with require('object-assign') or update package.json to NOT support node 0.12