When I'm scrolling around code, I sometimes put my mouse over the horizontal scrollbar and then the mouse wheel scrolls horizontally which is not what I'm used to.
More annoyingly, the two-finger scroll which allows me to scroll vertically or horizontally by moving my fingers up-and-down or left-and-right also changes to scrolling horizontally when going up-and-down if my mouse happens to be over a horizontal scrollbar.
The first problem is my preference but I think the second problem is a bug. How do I change these behaviours?
I'm using Ubuntu 15.04 Vivid with the default window manager, Unity.