WindowsPhone ListPicker does not "push down" other elements

Question

Code:

 <ScrollView>
     <StackLayout VerticalOptions="Start">
       <local:myListPicker x:Name="LP"></local:myListPicker>
       <Label Text="Push me"></Label>
       <Label Text="DOWN"></Label>
     </StackLayout>
    </ScrollView>

I added four Items to the ListPicker, when I tap on it, it opens, but only the first one can be seen, since it does not "push away" the two labels under it.

It looks like the ListPicker is "behind" the two labels, why is that and how to fix?

Additinol Info:

• ExpansionMode equals ExpansionMode.ExpansionAllowed.
• With 5 or more Items in the List it gets fullscreen (which is totally OK)