Fix: unable convert Slim to HTML

Before:
![image](https://cloud.githubusercontent.com/assets/5310542/5453385/a92130ce-8561-11e4-855b-e091075ad416.png)

After:
![image](https://cloud.githubusercontent.com/assets/5310542/5453370/870492ba-8561-11e4-93d8-72b724f0ac88.png)