New custom content type does not show in outcome options

I have been following the tutorial here: http://ift.tt/1BLqhoh to create a workflow with a custom workflow task, and have created a new custom content type, inheriting from the "Workflow Task(SharePoint 2013)" type.

I then go to create a workflow and add "Start a Task Process". in the Outcome Options section I should be able to see my new custom type in the drop-down for Task content type, but it's not there.

I have not hidden the % complete or Task Status columns.

What else do I need to do to get my new custom workflow task to appear in the drop-down list for Task content type?