Clojurians Log v2

I'm trying to add CORS support to Protojure, which uses a Pedestal stack on top of undertow. it looks like a correct :response map is being created, but then when the undertow integration starts trying to build the response, I get an IllegalStateException that the response has already started being sent. I'm not sure where to start looking to see how that might have happened or what part of my Pedestal stack started sending the response early.

is there some magic I'm not aware of when someone sets {:response {:status 200 ...}} on the context?