Click the app name next to the simulator/device selector at the top of Xcode. Going to Edit Schemes... and adding Environment Variable OS_ACTIVITY_MODE with value disable seems to get rid of this. Don't know why? Got this from https://developer.apple.com/forums/thread/702600?page=1#717626022

How/Why does this work?

I get the same thing but the simulator does not stop responding.

You can add syntactic sugar by adding a computed var with the same name to working example at the top In this example var formatter : NSDateFormatter { get { Constants.formatter } set { Constants.formatter = newValue } }