Disabling Mouse Wheel Clicking in Scene Window

Hello. For some weird reason, when I'm zoomed in on terrain, and I use the mouse middle/wheel button to move the camera around, it zooms out immediately when I release the button. I found out that when I just click the wheel, it does the same.

Is there any way to disable this behaviour? It's really annoying...

I've tried looking through the preferences but found nothing. I'm running windows 7 and unity 4.6.0