There is no Workflow App Part registered with custom Workflow Activity in SharePoint 2013 App

Good Day,

we're using a recently updated (to SharePoint 2013) installation of SharePoint Online.

I am using a developer site collection to create a prototype SharePoint app in Visual Studio 2012 utilizing the autohosted deployment model.

As soon as I add a custom workflow activity to the project, deployment fails with the error message:

"There is no Workflow App Part registered"

This sample project from Microsoft shows the same deployment error: http://code.msdn.microsoft.com/SharePoint-2013-workflow-41e5c0f9 

It seems as if the problem is known for on premise deployments and can be corrected using PowerShell: 

http://www.andrewconnell.com/blog/Updates-For-SP2013-Workflow

But what can I do with my SharePoint Online installation?

I am happy for any insight (if I can manage the Online installation by myself) as I could not find anything related to this problem for SharePoint online on the web.

Thanks,

Fabian