Vernacular and Xaml

I am trying to get vernacular working with Xaml.
A few people (including the TodoL10NVernacular sample) have recommended using:
<Label Text="{i18n:Translate Name}" />
The problem is this method is the vernacular tool won't extract the string.
I then tried to use the BindableProperty provided by Vernacular:

namespace:
xmlns:vernacular="clr-namespace:Vernacular.Xaml;assembly=Vernacular.Catalog.XamarinForms"
control:
<Label vernacular:Catalog.Message="Name">

This allows vernacular to extract the string. But the code won't run. When I try to create the page, I get an unhandled exception:
System.Reflection.TargetIncovationException: Exception has been thrown by the target of an invocation.

I'm using 1.3.1 Xamarin with 2.0 XLabs

Is the bindableproperty not supported, or am I defining something wrong?
The bindableproperty seems much cleaner than the TranslateExtension as it will also allow me to set the comments