When I try to add an extension to my Xcode project, I get the following warning: Activate “MyMonitor” scheme? This scheme has been created for the “(null)” target. Choose Activate to use this scheme for building and debugging. Schemes can be chosen in the toolbar or Product menu. I'm trying to understand a few things about this error: What exactly does the "(null)" target refer to? Could it be that Xcode is creating the scheme before the target is complete? Could this "(null)" target be the reason my code doesn't seem to be connecting properly to my app extension? How can I correct this issue? I ran into this during the process of trying to add a Device Activity Monitor Extension to my iOS project. Any hints are welcome, I have been stuck on this for too long.