ItemsControl SourceUpdated not firing

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C#

XAML

WPF

I have an ItemsControl that is bound to a collection like so:

<ItemsControl ItemsSource="{Binding Path=AllComponents, NotifyOnSourceUpdated=True, NotifyOnTargetUpdated=True}" x:Name="myItemsControl" SourceUpdated="Components_Updated">

Event Handler:

private void Components_Updated(object sender, DataTransferEventArgs e)
        {
            //stuff goes here
        }

The only problem is that the SourceUpdated event never fires when I add something to the collection. My handler never gets called.

Anyone know how to fix this?