diff --git a/app/src/main/kotlin/de/rochefort/childmonitor/DiscoverActivity.kt b/app/src/main/kotlin/de/rochefort/childmonitor/DiscoverActivity.kt
index b4aae6d..731d2f8 100644
--- a/app/src/main/kotlin/de/rochefort/childmonitor/DiscoverActivity.kt
+++ b/app/src/main/kotlin/de/rochefort/childmonitor/DiscoverActivity.kt
@@ -34,11 +34,11 @@ import android.widget.ListView
 import android.widget.Toast
 
 class DiscoverActivity : Activity() {
-    private var nsdManager: NsdManager? = null
+    private lateinit var nsdManager: NsdManager
     private var discoveryListener: DiscoveryListener? = null
     override fun onCreate(savedInstanceState: Bundle?) {
         Log.i(TAG, "ChildMonitor start")
-        nsdManager = this.getSystemService(NSD_SERVICE) as NsdManager
+        this.nsdManager = this.getSystemService(NSD_SERVICE) as NsdManager
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_discover)
         val discoverChildButton = findViewById<Button>(R.id.discoverChildButton)
@@ -94,7 +94,7 @@ class DiscoverActivity : Activity() {
         this.discoveryListener?.let {
             this.discoveryListener = null
             Log.i(TAG, "Unregistering monitoring service")
-            this.nsdManager!!.stopServiceDiscovery(it)
+            this.nsdManager.stopServiceDiscovery(it)
         }
         super.onDestroy()
     }
diff --git a/app/src/main/kotlin/de/rochefort/childmonitor/ListenService.kt b/app/src/main/kotlin/de/rochefort/childmonitor/ListenService.kt
index 088fc77..14e5041 100644
--- a/app/src/main/kotlin/de/rochefort/childmonitor/ListenService.kt
+++ b/app/src/main/kotlin/de/rochefort/childmonitor/ListenService.kt
@@ -43,7 +43,7 @@ class ListenService : Service() {
     private val bufferSize = AudioTrack.getMinBufferSize(frequency, channelConfiguration, audioEncoding)
     private val byteBufferSize = bufferSize * 2
     private val binder: IBinder = ListenBinder()
-    private var notificationManager: NotificationManager? = null
+    private lateinit var notificationManager: NotificationManager
     private var listenThread: Thread? = null
     val volumeHistory = VolumeHistory(16384)
     var childDeviceName: String? = null
@@ -79,7 +79,7 @@ class ListenService : Service() {
 
         // Cancel the persistent notification.
         val NOTIFICATION = R.string.listening
-        notificationManager!!.cancel(NOTIFICATION)
+        notificationManager.cancel(NOTIFICATION)
         ServiceCompat.stopForeground(this, ServiceCompat.STOP_FOREGROUND_REMOVE)
         // Tell the user we stopped.
         Toast.makeText(this, R.string.stopped, Toast.LENGTH_SHORT).show()
@@ -115,7 +115,7 @@ class ListenService : Service() {
                     "Foreground Service Channel",
                     NotificationManager.IMPORTANCE_DEFAULT
             )
-            notificationManager!!.createNotificationChannel(serviceChannel)
+            notificationManager.createNotificationChannel(serviceChannel)
         }
     }
 
diff --git a/app/src/main/kotlin/de/rochefort/childmonitor/MonitorService.kt b/app/src/main/kotlin/de/rochefort/childmonitor/MonitorService.kt
index 3e5c739..d29128c 100644
--- a/app/src/main/kotlin/de/rochefort/childmonitor/MonitorService.kt
+++ b/app/src/main/kotlin/de/rochefort/childmonitor/MonitorService.kt
@@ -41,12 +41,12 @@ import java.net.Socket
 
 class MonitorService : Service() {
     private val binder: IBinder = MonitorBinder()
-    private var nsdManager: NsdManager? = null
+    private lateinit var nsdManager: NsdManager
     private var registrationListener: RegistrationListener? = null
     private var currentSocket: ServerSocket? = null
     private var connectionToken: Any? = null
     private var currentPort = 0
-    private var notificationManager: NotificationManager? = null
+    private lateinit var notificationManager: NotificationManager
     private var monitorThread: Thread? = null
     private var monitorActivity: MonitorActivity? = null
     fun setMonitorActivity(monitorActivity: MonitorActivity?) {
@@ -195,7 +195,7 @@ class MonitorService : Service() {
                 Log.e(TAG, "Unregistration failed: $errorCode")
             }
         }
-        nsdManager!!.registerService(
+        nsdManager.registerService(
                 serviceInfo, NsdManager.PROTOCOL_DNS_SD, registrationListener)
     }
 
@@ -203,7 +203,7 @@ class MonitorService : Service() {
         this.registrationListener?.let {
             this.registrationListener = null
             Log.i(TAG, "Unregistering monitoring service")
-            this.nsdManager!!.unregisterService(it)
+            this.nsdManager.unregisterService(it)
         }
     }
 
@@ -214,7 +214,7 @@ class MonitorService : Service() {
                     "Foreground Service Channel",
                     NotificationManager.IMPORTANCE_DEFAULT
             )
-            this.notificationManager!!.createNotificationChannel(serviceChannel)
+            this.notificationManager.createNotificationChannel(serviceChannel)
         }
     }
 
@@ -246,7 +246,7 @@ class MonitorService : Service() {
         }
 
         // Cancel the persistent notification.
-        this.notificationManager!!.cancel(R.string.listening)
+        this.notificationManager.cancel(R.string.listening)
         ServiceCompat.stopForeground(this, ServiceCompat.STOP_FOREGROUND_REMOVE)
         // Tell the user we stopped.
         Toast.makeText(this, R.string.stopped, Toast.LENGTH_SHORT).show()