IndexRoute issues with react-router

router.js

const routes = (
  <Route component={ App } path="/">
    <Route component={ Child } path="child/:id">
      <Route component={ GrandChild } path="grandchild" />
      <IndexRoute component={ IndexGrandChild } />
    </Route>
  </Route>
);


// ...
// In a component, which should I use? 
<IndexLink to={ `child/${ id }` } />
// or
<Link to={ `child/${ id }` />

// Using IndexLink does not render any links, where as Link does and works.

// Getting strange errors with Link `Cannot read property '_currentElement' of null`
// when I try use *other* Links

Either usage is "correct".

Given this url:

child/123

Both links should be "active"

but at child/123/grandchild IndexLink should not be active, but Link still will.