webpack 2 doesn't work on IE11?

I have a very basic javascript-project that uses webpack (^2.6.0) as a module bundler. There is one dependency as a vendor module, and I have one entry point. My configuration is as follows:

const path = require('path');
const webpack = require('webpack');

module.exports = {
    entry: {
        bundle: './modules/main.js',
        vendor: ['react']
    },
    output: {
        path: path.join(__dirname, 'build'),
        filename: '[name].js',
        chunkFilename: '[id].js'
    },
    plugins: [
        new webpack.optimize.CommonsChunkPlugin({
            name: "vendor"
        })
    ]
};

This creates the bundles bundle.js and vendor.js. The vendor-bundle also contains the webpack-bootstrap-code, which is loaded BEFORE any of my modules are loaded. Now, inspecing that bootstrapping code reveals that on line 40, webpack generated

/******/    var resolvedPromise = new Promise(function(resolve) { resolve(); });

Unfortunately, Promise is not available on IE11, and even if you include a polyfill that includes Promise (with e.g. import 'babel-polyfill') as the first thing in the entry point, or even as its own entry point, it will never get executed before the bootstrapping code runs, which means I can't use this code on IE11 unless I include a Promise-polyfill manually before my webpack-bundles. Unsurprisingly, IE11 throws a Promise is not defined error before I even get to any of my code or even to the vendor bundle.

Am I missing something here or is this the expected behavior? I can't find anything in the webpack docs to counteract this issue.