vue-jest: TypeError: Cannot read property 'lang' of null

I am trying out your webpack template to use jest for unit testing in a new little app and am getting this error when running npm run unit:

 FAIL  test/unit/specs/App.spec.js
  ● Test suite failed to run

    TypeError: Cannot read property 'lang' of null

      at processScript (node_modules/jest-vue/lib/process.js:13:17)
      at Object.module.exports [as process] (node_modules/jest-vue/lib/process.js:27:18)
      at Object.<anonymous> (test/unit/specs/App.spec.js:1:114)

I reduced the file to an absolute minimum and I’m still getting the error.

App.spec.js

import App from '@/App'

App.vue

<template>
  <div id="app">
  </div>
</template>

package.json

...
"jest": "^21.2.0",
"jest-vue": "^0.7.0",
...

This is the offending line in jest-vue/lib/process.js:

function processScript (scriptPart) {
  if (scriptPart.lang === 'typescript' || scriptPart.lang === 'ts') {

Which seems to make sense since I do not define a lang attribute on my script tags.