react-hot-loader: Error when using v4

Description

Error on hot reload when rendering certain parts of the app.

Actual behavior

Blank page, error in browser console: (fixed in beta 4)

hotReplacementRender.js:118 Uncaught TypeError: Cannot read property 'length' of undefined
    at mergeInject (hotReplacementRender.js:118)
    at flow.forEach (hotReplacementRender.js:162)
    at Array.forEach (<anonymous>)
    at hotReplacementRender (hotReplacementRender.js:139)
    at next (hotReplacementRender.js:151)
    at flow.forEach (hotReplacementRender.js:168)
    at Array.forEach (<anonymous>)
    at hotReplacementRender (hotReplacementRender.js:139)
    at next (hotReplacementRender.js:151)
    at flow.forEach (hotReplacementRender.js:168)

react-dom.development.js:9747 The above error occurred in the <AppContainer> component:
    in AppContainer (created by HotExportedApp)
    in HotExportedApp

Consider adding an error boundary to your tree to customize error handling behavior.
Visit https://fb.me/react-error-boundaries to learn more about error boundaries.

Depending on the file I modify I also sometimes get this error (before the others), but I’m not sure if it’s related:

React-stand-in: Updated class  Connect(SomeContainer) contains native or bound function  
notifyNestedSubs ƒ notifyNestedSubs() {
    this.listeners.notify();
  } . Unable to reproduce, use arrow functions instead.

Environment

React Hot Loader version: 4.0.0-beta.3

React version: 16.2.0

node -v: 9.3.0

yarn -v: 1.3.2

Operating system: Windows 10

Browser and version: Chrome 63

Webpack is running via webpack-dev-middleware in WSL (no errors in terminal).