Doesn't appear to support Mask Path animation

[echolock]

This script doesn't appear to support Mask Path animation in AE CC 2015.2. When I select the Mask Path property and click 'Add Property', it brings up an alert saying "Doesn't appear to support Mask Path animation", then another box pops up with "Curve name:" and it looks like it's adding it but when I click okay, it doesn't get added to the list.