Access External List with SharePoint 2013 Workflow

In a SP 2010 designer workflow you could access/update an SQL table using an External List (ECT).

http://msdn.microsoft.com/en-us/library/ff394479(v=office.14).aspx

When I attempt to do the same thing in an SP 2013 workflow the External Lists don't show up in the Data Source drop down. Steps:

1. Create a test SQL table
2. Using SP Designer 2013, create an External Content Type with all operations (Create, Read Item...)
3. Create an External List from the test ECT
4. Using SP Designer 2013 create a list workflow (against a standard SP list i.e. a task list)
5. Add a Create item or Update item action
6. Click 'this list' and look for the External List using the List drop down
7. Issue: the External List is not in the List drop down

I can't find any references to this feature being deprecated in 2013.

Any assistance will be greatly appreciated.