ish* attributes are killing my 2.5.4 DITA OT builds. How do I handle them?

My DITA OT publishing events are failing because the files extracted from the content store contain ish* attributes, such as "ishlabelxpath".

I suspect there's an action in publishing that I'm missing in the publishing chain.

My client's KnowledgeCenter (hasn't been upgraded to Tridion) has been producing output using several different 1.x OTs with many different plugins.

One wrinkle is that we're adding a 2.5.4 OT to the Publishing Service.

Everything works great, right up to when the OT starts. The OT's genlist pipeline fails with a parsing error when it encounters the ishlablexpath attribute.

Where are these attributes normally handled in the Pubishing Service? Is there a step I'm missing that adds the attribute to the DTD?