Swift Singleton Memory Leak - singleton

Question

I'm using a singleton as a container for localization strings, dictionary keys, and notification names used throughout the app. It is initialized as follows:
class ConstantsManager {
private init() {}
class var sharedInstance: ConstantsManager {
struct Static {
static let instance: ConstantsManager! = ConstantsManager()
}
return Static.instance
}
let localization = "NSLocalizedString(etc.)"
let dictKey = "aKey"
let notificationName = Notification.Name("name")
}
The first use of the singleton occurs in AppDelegate's application(_ application: didFinishLaunchingWithOptions:). When Instruments / Leaks reaches
let manager = ConstantsManager.sharedInstance
a leak is indicated. Does the call tree below indicate that initialization is occurring twice? I'm wondering if the properties associated with a second initialization represent the leak. Strangely, the leak doesn't occur on the simulator. (I'm using Xcode 8.2.1 and OS X 10.12.3 for iOS 10.2 deployment.)
Bytes Used # Leaks Symbol Name
448 Bytes 100.0% 14 ConstantsManager.init() -> ConstantsManager
448 Bytes 100.0% 14 ConstantsManager.__allocating_init() -> ConstantsManager
448 Bytes 100.0% 14 globalinit_33_8D935C4E2193156DAA2AB3DF99F55E80_func0
448 Bytes 100.0% 14 static ConstantsManager.(sharedInstance.getter).(Static #1).instance.unsafeMutableAddressor
448 Bytes 100.0% 14 static ConstantsManager.sharedInstance.getter
448 Bytes 100.0% 14 AppDelegate.registerUserDefaults() -> ()
448 Bytes 100.0% 14 AppDelegate.application(UIApplication, didFinishLaunchingWithOptions : [UIApplicationLaunchOptionsKey : Any]?) -> Bool
448 Bytes 100.0% 14 #objc AppDelegate.application(UIApplication, didFinishLaunchingWithOptions : [UIApplicationLaunchOptionsKey : Any]?) -> Bool
448 Bytes 100.0% 14 main