Yes that what that! A tricky faint :)
I believed that was in the Options / General dialog and don't find it!
Maybe must be in General Options or View?

Hi Pilou, well it is actually in both!

In the Options dialog, it is with the rest of the viewport-related options under Options > View:



I put it additionally into the View side pane palette to make for quicker access if you wanted to turn it on or off repeatedly while modeling.

- Michael

So I was not very well awake! :)