Yup, I'm getting the same issue using the following steps: Running macOS 10.15.5 Generated a new test project in Xcode 11 ( to set deployment target to iOS 13.5 ) Opened it in Xcode 12 beta Run and get a crash in simulator and on a real device until I remove the conditional or change LazyHStack/LazyVStack to HStack/VStack/Text..etc Test project is just this code here: struct ContentView: View {   var body: some View {     VStack {       Text("Hello, World!")               if #available(iOS 14.0, *) {         LazyVStack {           Text("ios14 1")           Text("ios14 2")         }       } else {         HStack {           Text("ios13 1")           Text("ios13 2")         }       }     }         } } struct ContentView_Previews: PreviewProvider {   static var previews: some View {     ContentView()   } } lldb bt output - https://developer.apple.com/forums/content/attachment/d5732753-7d2c-4af2-ba3f-a355a5fe590e