Azure Cloud Service Project opens two browser windows on startup when debugging

I have a VS2013 Update 3 solution with one Azure Cloud Service Project, which has one Web Role / ASP.Net project, and later on Don't Open Page. selected under its Properties> Web tab, but whenever I run Azure CS.ccproj for debugging (it is later installed as a startup project), two (more than one) Windows browser windows open each time.

Does anyone know where I can turn this off, or at least set it to only one window? It works with Azure SDK 2.4, I am using IIS Express and (Azure) Emulator Express.