Fix thumbnail for dynamic/slow

Before:

![screen shot 2014-10-21 at 18 17 51](https://cloud.githubusercontent.com/assets/1001642/4723263/4befcc90-5946-11e4-8745-ebd8283022ec.png)

After:

![screen shot 2014-10-21 at 18 17 57](https://cloud.githubusercontent.com/assets/1001642/4723266/50e5bc82-5946-11e4-9b20-fc3b9f76fb59.png)