Selection goes crazy when you start dragging and then use mouse wheel

Start:

![image](https://cloud.githubusercontent.com/assets/2193314/15738918/78877e50-2862-11e6-91bc-17fbcb4ab59b.png)

Mouse wheel up:

![image](https://cloud.githubusercontent.com/assets/2193314/15738936/8ae2c244-2862-11e6-99d0-5e9f72df7c61.png)
