How do I make Pale Moon allow "middle-click-scroller" even when the page has no scrollbars?

I frequently middle-click webpages, hold down the mouse button and slowly scroll around.

When a webpage has no vertical scrollbar, usually meaning that the contents fit in one screen, middle-clicking the webpage does nothing in Pale Moon (and I think Firefox).

I want it to always display the little visual thing, even if it just sits there and nothing happens. The fact that it does not show up “sometimes” makes me feel uncomfortable. Even though it has no practical difference, there is a psychological aspect to this. Is it possible to force it to always display when I middle-click the (empty part of the) page?