Storybook: ModuleBuildError: Module build failed: SyntaxError: Unexpected token

Just installed storybook into my create-react-app project, and am trying to start storybook for the first time. I followed the manual setup verbatim. Looks like webpack is failing somehow. The error output is huge, but the relevant section seems to be:

 [ ModuleBuildError: Module build failed: SyntaxError: Unexpected token (7:8)

           5 | storiesOf('Button', module)
           6 |     .add('with text', () => (
        >  7 |         <button onClick={action('clicked')}>Hello Button</button>
             |         ^
           8 |     ))
           9 |     .add('with some emoji', () => (
          10 |         <button onClick={action('clicked')}>😀 😎 👍 💯</button>

React version is 15.6.1.

I used the default config.json specified in the instructions, and am only loading the example Button story (none of my own modules).

I'm no webpack expert, so not sure what's going on here.