We used capitalized names here to communicate the fact that they are constructors. Since they are still constructors within the scope of this function, we should maintain that convention:

```javascript
(function(Stopwatch, Panel) {
// ...
}(Stopwatch, Panel));
```

Unfortunately, you'll have to update your references to `panel`, but you *won't* have to change `Panel` (notice how `panel` is currently unused)