Label LineBreakMode WordWrap behaves as CharacterWrap when using Bindings

I have a Label in which the Text or FormattedText property is populated with a binding towards a property on my ViewModel. The LineBreakMode has been set to WordWrap, but it behaves as a CharacterWrap. Replacing the LineBreakMode with Head/Middle/TailTruncation or NoWrap works as expected. When the binding is replaced by just a long text without a binding, then it also works as expected.

<!-- Working without binding -->
<Label
    HorizontalOptions="Fill" VerticalOptions="Center"
    YAlign="Center"
    LineBreakMode="WordWrap"
    FontSize="12"
    Text="This is a very long text that should be put over multiple lines to ensure that no characterwrap occurs, but that wordwrap does."/>

<!-- NOT working with binding -->
<Label
    HorizontalOptions="Fill" VerticalOptions="Center"
    YAlign="Center"
    LineBreakMode="WordWrap"
    FontSize="12"
    Text="{Binding LongText}"/>

<!-- Desired situation - NOT working with binding -->
<Label
    HorizontalOptions="Fill" VerticalOptions="Center"
    YAlign="Center"
    LineBreakMode="WordWrap"
    FontSize="12"
    FormattedText="{Binding LongText, Converter={StaticResource FormattedStringValueConverter}}"/>

As context, I'm using this inside a StackLayout within a ViewCell that is shown inside a ListView, but that doesn't seem to effect this case.
This occurs on iOS, haven't been able to try it on Android yet...

I'm on Xamarin.Forms 1.5.1.6471