webpack compiler doesn't convert the es6 syntax to the older versions's at all

Here is the snapshot of a part of my script after compiling:

I don’t understand that why doesn’t it convert new.target to this.constructor?

Example:

class IList {
  constructor() {
    console.log('compare using new.target:', new.target === IList);
    console.log('compare using this.constructor:', this.constructor === IList);
  }
}

new IList();

I want it does that because I can use this.constructor in the browsers which don’t support for es6 while new.target requires.

Should I report it to webpack team?

UPDATE:

webpack.config.js:

let webpack = require('webpack'),
    path = require('path'),
    BabiliPlugin = require("babili-webpack-plugin");

module.exports = {
    entry: {
        'site': './assets/js/site',
        'site.min': './assets/js/site'
    },
    output: {
        publicPath: '/js/',
        path: path.join(__dirname, '/wwwroot/js/'),
        filename: '[name].js'
    },
    module: {
        loaders: [
            {
                exclude: /node_modules/,
                loader: 'babel-loader',
                query: {
                    presets: ['es2015', 'stage-1']
                }
            }
        ]
    },
    plugins: [
        new BabiliPlugin({}, {
            test: //.min/.js$/
        }),
        new webpack.ProvidePlugin({
            $: 'jquery',
            jQuery: 'jquery'
        })
    ]
};

It looks like this issue is solved in Babel 7. See https://github.com/babel/babel/pull/5906

Seems like it’s included in the builds of the pre-release: https://github.com/babel/babel/releases