Listview - Separator do not display while they do when I pull the list

Hi,

Create a new Xamarin Forms project. Add a listview as the sole element of your MainPage content. Try in iOS simulator: no separators (while I made them green...).
Pull the list and you'll see the separators. Once the pull is over, the separors disapear again.
A bug?
I'm using lastest stable xamarin forms.
Tks.

François