Warnings when using custom prop to force update

I am using a custom prop to force my list to re-render, as recommended [in the readme](https://github.com/clauderic/react-tiny-virtual-list#common-issues-with-purecomponent). However, doing so causes me this warning:

> Warning: React does not recognize the `isScrolling` prop on a DOM element. If you intentionally want it to appear in the DOM as a custom attribute, spell it as lowercase `isscrolling` instead. If you accidentally passed it from a parent component, remove it from the DOM element.

(my prop is called `isScrolling`)