Indentation!  The `if` should be aligned with the `@ruby_gem`.

Also, for flash notices:
1. I'd put the notice first, above the `redirect_to` line.  Otherwise you might run into errors where it doesn't show up on the page you're redirected to, but persists for an additional request.  You can also use the syntax:

```ruby
redirect_to @ruby_gem, notice: "Successfully added gem"
```
2. It's generally a good idea to flash an error notice, too -- I'd add one to your `else` condition.