when you scroll one notch the hot bare square doesn't move

What I expected to happen was...:

The selected square in the hotbar should move when i scroll one notch on my mouse
What actually happened was...:

it doesn't move at all. You need to scroll several times to select another square in the hotbar.

Steps to Reproduce:
1. Join a world or a server (it's need to be on a mac)
2. Scroll to choose what you want to hold