UglifyJs fails after upgrade to relay-runtime 10.0.0

After upgrading `relay-runtime` and `relay-compiler` from 9.1.0 to 10.0.0 I started to get the following error from `UglifyJs`:

`ERROR in bundle.js from UglifyJs
Unexpected token: operator «*», expected: punc «(» [./node_modules/relay-runtime/lib/store/RelayModernStore.js:639,0][bundle.js:56627,28]`

Uglify is called from webpack config like so:
```
...
devtool: 'source-map',
plugins: [
new UglifyJSPlugin({
sourceMap: true
}),
...
```

Any ideas / workarounds?