             return
         }
 
-        dispatch_sync(zephyrQueue) {
+        dispatch_sync(zephyrKeyQueue) {
 
             if let index = self.registeredObservationKeys.indexOf(key) {
 

        // Synchronize changes if key is monitored and if key is currently registered to respond to changes
        if monitoredKeys.contains(keyPath) {

            dispatch_async(zephyrQueue, {
                if self.registeredObservationKeys.contains(keyPath) {
                    if object is NSUserDefaults {
                        NSUserDefaults.standardUserDefaults().setObject(NSDate(), forKey: self.ZephyrSyncKey)

            return
        }

        dispatch_sync(zephyrKeyQueue) {

            if !self.registeredObservationKeys.contains(key) {

