CSS :hover pseudo-class behavior

Hello.
I want to set menu (top level) background for a GTK3 application in gtk.css like this:

menubar > menuitem:hover {background: blue; }

The problem is, the background doesn’t change when mouse hovers over the particular menu item, but only when I click/open the menu.

Is it possible to make menu background change when mouse hovers over the menuitem (using gtk.css)?