Webpack not compiling files on Heroku - django

Question

I want to use Webpack to compile files for my Django app on Heroku, and am using webpack-bundle-tracker to keep track of the modules created in webpack-stats.json. When I run webpack locally, it compiles all the files and bundles them into the output directory, no problem. But when I run webpack on Heroku, it shows me that all the chunks were emitted, but none of the files appear in the output directory. When I check the content of webpack-stats.json it always says "status" : "compiling".
Here's the content of my webpack.config.js.
var path = require('path')
var webpack = require('webpack')
var BundleTracker = require('webpack-bundle-tracker')
module.exports = {
context: __dirname,
entry: './assets/js/index',
output: {
path: path.resolve('./assets/bundles/'),
filename: '[name].js',
},
plugins: [
new BundleTracker({filename: './webpack-stats.json'}),
],
module: {
loaders: [
{ test: /\.jsx?$/,
exclude: /node_modules/,
loader: 'babel-loader',
query: {
presets: ['react']
}
}
]
},
resolve: {
modulesDirectories: ['node_modules', 'bower_components'],
extensions: ['', '.js', '.jsx'],
},
}
I want webpack to bundle my assets the same way on heroku as it does on my local machine. How can I accomplish that?