storybook: addon-storysource: not working without chaining

Storysource addon does not detect stories when they are created without chaining:

const stories = storiesOf('MyCoolButton', module);

stories.add('first story', () => (
  ...
));

stories.add('second story', () => (
  ...
));

stories.add('third story', () => (
  ...
));

Tested on @storybook/react@5.0.1, @storybook/addon-storysource@5.0.1