TreeListView - Expansion arrow not shown

Hi,

so im trying to use the Treelistview and i followed to examples to build a list of items.

All is working fine, but for some reason i cannot see the expansion arrow. 

I am able to double click the items to expand, but no arrow is shown.

What is weird, is that it seems present since i can single click expand the node by pressing on the left of the item (where the arrow SHOULD be and behaves as if i clicked on it).

Any idea what is wrong?

Here is my tree view code:

<grids:TreeListView x:Name="treeListView"
RootItem="{Binding ElementName=DefaultLayout, Path=CircuitItemsRoot}"
AreColumnHeadersVisible="False">
<grids:TreeListView.ItemAdapter>
<grids:TreeListBoxItemAdapter
ChildrenBinding="{Binding Childs, Mode=OneTime}"
IsExpandedBinding="{Binding IsExpanded, Mode=TwoWay}"
/>
</grids:TreeListView.ItemAdapter>
<grids:TreeListView.Columns>
<grids:TreeListViewColumn Header="Name" Width="*" MaxWidth="300">
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Image Source="{Binding Image}" Height="16"/>
<TextBlock Text="{Binding Name}" Margin="5,0,0,0"/>
</StackPanel>
</DataTemplate>
</grids:TreeListViewColumn>
<grids:TreeListViewColumn Header="Visibility" Width="auto" HeaderHorizontalAlignment="Right" CellHorizontalAlignment="Right" >
<DataTemplate>
<CheckBox IsChecked="{Binding IsVisible}"/>
</DataTemplate>
</grids:TreeListViewColumn>
</grids:TreeListView.Columns>
</grids:TreeListView>