diff --git a/app/src/main/java/org/linphone/activities/assistant/viewmodels/AccountLoginViewModel.kt b/app/src/main/java/org/linphone/activities/assistant/viewmodels/AccountLoginViewModel.kt
index 4b4aff03d..7212f5c08 100644
--- a/app/src/main/java/org/linphone/activities/assistant/viewmodels/AccountLoginViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/assistant/viewmodels/AccountLoginViewModel.kt
@@ -78,12 +78,12 @@ class AccountLoginViewModel(accountCreator: AccountCreator) : AbstractPhoneViewM
     private var proxyConfigToCheck: ProxyConfig? = null
 
     private val coreListener = object : CoreListenerStub() {
-        override fun onRegistrationStateChanged(
-            core: Core,
-            cfg: ProxyConfig,
-            state: RegistrationState,
-            message: String?
-        ) {
+            override fun onRegistrationStateChanged(
+                core: Core,
+                cfg: ProxyConfig,
+                state: RegistrationState,
+                message: String
+            ) {
             if (cfg == proxyConfigToCheck) {
                 Log.i("[Assistant] [Account Login] Registration state is $state: $message")
                 waitForServerAnswer.value = false
diff --git a/app/src/main/java/org/linphone/activities/assistant/viewmodels/GenericLoginViewModel.kt b/app/src/main/java/org/linphone/activities/assistant/viewmodels/GenericLoginViewModel.kt
index 53741d087..774d01726 100644
--- a/app/src/main/java/org/linphone/activities/assistant/viewmodels/GenericLoginViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/assistant/viewmodels/GenericLoginViewModel.kt
@@ -65,7 +65,7 @@ class GenericLoginViewModel(private val accountCreator: AccountCreator) : ViewMo
             core: Core,
             cfg: ProxyConfig,
             state: RegistrationState,
-            message: String?
+            message: String
         ) {
             if (cfg == proxyConfigToCheck) {
                 Log.i("[Assistant] [Generic Login] Registration state is $state: $message")
diff --git a/app/src/main/java/org/linphone/activities/assistant/viewmodels/QrCodeViewModel.kt b/app/src/main/java/org/linphone/activities/assistant/viewmodels/QrCodeViewModel.kt
index 69d6d2bc8..b5daaec35 100644
--- a/app/src/main/java/org/linphone/activities/assistant/viewmodels/QrCodeViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/assistant/viewmodels/QrCodeViewModel.kt
@@ -33,9 +33,9 @@ class QrCodeViewModel : ViewModel() {
     val showSwitchCamera = MutableLiveData<Boolean>()
 
     private val listener = object : CoreListenerStub() {
-        override fun onQrcodeFound(core: Core, result: String) {
+        override fun onQrcodeFound(core: Core, result: String?) {
             Log.i("[QR Code] Found [$result]")
-            qrCodeFoundEvent.postValue(Event(result))
+            if (result != null) qrCodeFoundEvent.postValue(Event(result))
         }
     }
 
diff --git a/app/src/main/java/org/linphone/activities/assistant/viewmodels/RemoteProvisioningViewModel.kt b/app/src/main/java/org/linphone/activities/assistant/viewmodels/RemoteProvisioningViewModel.kt
index 6a09416e3..0e5d13c34 100644
--- a/app/src/main/java/org/linphone/activities/assistant/viewmodels/RemoteProvisioningViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/assistant/viewmodels/RemoteProvisioningViewModel.kt
@@ -38,7 +38,7 @@ class RemoteProvisioningViewModel : ViewModel() {
     val fetchSuccessfulEvent = MutableLiveData<Event<Boolean>>()
 
     private val listener = object : CoreListenerStub() {
-        override fun onConfiguringStatus(core: Core, status: ConfiguringState, message: String?) {
+        override fun onConfiguringStatus(core: Core, status: ConfiguringState, message: String) {
             fetchInProgress.value = false
             when (status) {
                 ConfiguringState.Successful -> {
diff --git a/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsFadingViewModel.kt b/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsFadingViewModel.kt
index 646dd5e2c..5e1447d00 100644
--- a/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsFadingViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsFadingViewModel.kt
@@ -50,7 +50,7 @@ class ControlsFadingViewModel : ViewModel() {
             core: Core,
             call: Call,
             state: Call.State,
-            message: String?
+            message: String
         ) {
             if (state == Call.State.StreamsRunning || state == Call.State.Updating || state == Call.State.UpdatedByRemote) {
                 val isVideoCall = coreContext.isVideoCallOrConferenceActive()
diff --git a/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsViewModel.kt b/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsViewModel.kt
index f13c5bc42..8df5b9d59 100644
--- a/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/call/viewmodels/ControlsViewModel.kt
@@ -106,7 +106,7 @@ class ControlsViewModel : ViewModel() {
             core: Core,
             call: Call,
             state: Call.State,
-            message: String?
+            message: String
         ) {
             if (state == Call.State.StreamsRunning) isVideoUpdateInProgress.value = false
 
diff --git a/app/src/main/java/org/linphone/activities/call/viewmodels/StatisticsListViewModel.kt b/app/src/main/java/org/linphone/activities/call/viewmodels/StatisticsListViewModel.kt
index 775a9cb07..08b8def5e 100644
--- a/app/src/main/java/org/linphone/activities/call/viewmodels/StatisticsListViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/call/viewmodels/StatisticsListViewModel.kt
@@ -34,7 +34,7 @@ class StatisticsListViewModel : ViewModel() {
             core: Core,
             call: Call,
             state: Call.State,
-            message: String?
+            message: String
         ) {
             if (state == Call.State.End || state == Call.State.Error) {
                 val newList = arrayListOf<CallStatisticsViewModel>()
diff --git a/app/src/main/java/org/linphone/activities/call/viewmodels/StatusViewModel.kt b/app/src/main/java/org/linphone/activities/call/viewmodels/StatusViewModel.kt
index f303628a5..981eb3a3c 100644
--- a/app/src/main/java/org/linphone/activities/call/viewmodels/StatusViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/call/viewmodels/StatusViewModel.kt
@@ -47,7 +47,7 @@ class StatusViewModel : StatusViewModel() {
             core: Core,
             call: Call,
             on: Boolean,
-            authenticationToken: String
+            authenticationToken: String?
         ) {
             if (call.currentParams.mediaEncryption == MediaEncryption.ZRTP && !call.authenticationTokenVerified) {
                 showZrtpDialogEvent.value = Event(call)
@@ -60,7 +60,7 @@ class StatusViewModel : StatusViewModel() {
             core: Core,
             call: Call,
             state: Call.State,
-            message: String?
+            message: String
         ) {
             if (call == core.currentCall) {
                 updateEncryptionInfo(call)
diff --git a/app/src/main/java/org/linphone/activities/main/chat/viewmodels/DevicesListViewModel.kt b/app/src/main/java/org/linphone/activities/main/chat/viewmodels/DevicesListViewModel.kt
index 14ddbb4ae..cb47fbb64 100644
--- a/app/src/main/java/org/linphone/activities/main/chat/viewmodels/DevicesListViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/main/chat/viewmodels/DevicesListViewModel.kt
@@ -39,19 +39,19 @@ class DevicesListViewModel(private val chatRoom: ChatRoom) : ViewModel() {
     val participants = MutableLiveData<ArrayList<DevicesListGroupViewModel>>()
 
     private val listener = object : ChatRoomListenerStub() {
-        override fun onParticipantDeviceAdded(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onParticipantDeviceAdded(chatRoom: ChatRoom, eventLog: EventLog) {
             updateParticipants()
         }
 
-        override fun onParticipantDeviceRemoved(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onParticipantDeviceRemoved(chatRoom: ChatRoom, eventLog: EventLog) {
             updateParticipants()
         }
 
-        override fun onParticipantAdded(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onParticipantAdded(chatRoom: ChatRoom, eventLog: EventLog) {
             updateParticipants()
         }
 
-        override fun onParticipantRemoved(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onParticipantRemoved(chatRoom: ChatRoom, eventLog: EventLog) {
             updateParticipants()
         }
     }
diff --git a/app/src/main/java/org/linphone/activities/main/chat/viewmodels/GroupInfoViewModel.kt b/app/src/main/java/org/linphone/activities/main/chat/viewmodels/GroupInfoViewModel.kt
index e3b016baa..21bd4a7e8 100644
--- a/app/src/main/java/org/linphone/activities/main/chat/viewmodels/GroupInfoViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/main/chat/viewmodels/GroupInfoViewModel.kt
@@ -70,19 +70,19 @@ class GroupInfoViewModel(val chatRoom: ChatRoom?) : ErrorReportingViewModel() {
             }
         }
 
-        override fun onSubjectChanged(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onSubjectChanged(chatRoom: ChatRoom, eventLog: EventLog) {
             subject.value = chatRoom?.subject
         }
 
-        override fun onParticipantAdded(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onParticipantAdded(chatRoom: ChatRoom, eventLog: EventLog) {
             updateParticipants()
         }
 
-        override fun onParticipantRemoved(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onParticipantRemoved(chatRoom: ChatRoom, eventLog: EventLog) {
             updateParticipants()
         }
 
-        override fun onParticipantAdminStatusChanged(chatRoom: ChatRoom?, eventLog: EventLog?) {
+        override fun onParticipantAdminStatusChanged(chatRoom: ChatRoom, eventLog: EventLog) {
             val admin = chatRoom?.me?.isAdmin ?: false
             isMeAdmin.value = admin
             meAdminChangedEvent.value = Event(admin)
diff --git a/app/src/main/java/org/linphone/activities/main/chat/viewmodels/ImdnViewModel.kt b/app/src/main/java/org/linphone/activities/main/chat/viewmodels/ImdnViewModel.kt
index ebdebe520..7bc782089 100644
--- a/app/src/main/java/org/linphone/activities/main/chat/viewmodels/ImdnViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/main/chat/viewmodels/ImdnViewModel.kt
@@ -42,8 +42,8 @@ class ImdnViewModel(private val chatMessage: ChatMessage) : ViewModel() {
 
     private val listener = object : ChatMessageListenerStub() {
         override fun onParticipantImdnStateChanged(
-            message: ChatMessage?,
-            state: ParticipantImdnState?
+            message: ChatMessage,
+            state: ParticipantImdnState
         ) {
             updateParticipantsLists()
         }
diff --git a/app/src/main/java/org/linphone/activities/main/dialer/viewmodels/DialerViewModel.kt b/app/src/main/java/org/linphone/activities/main/dialer/viewmodels/DialerViewModel.kt
index ddba352f2..d4365a69a 100644
--- a/app/src/main/java/org/linphone/activities/main/dialer/viewmodels/DialerViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/main/dialer/viewmodels/DialerViewModel.kt
@@ -80,7 +80,7 @@ class DialerViewModel : LogsUploadViewModel() {
             core: Core,
             call: Call,
             state: Call.State,
-            message: String?
+            message: String
         ) {
             atLeastOneCall.value = core.callsNb > 0
         }
diff --git a/app/src/main/java/org/linphone/activities/main/sidemenu/viewmodels/SideMenuViewModel.kt b/app/src/main/java/org/linphone/activities/main/sidemenu/viewmodels/SideMenuViewModel.kt
index 95acd6617..8c9a645fe 100644
--- a/app/src/main/java/org/linphone/activities/main/sidemenu/viewmodels/SideMenuViewModel.kt
+++ b/app/src/main/java/org/linphone/activities/main/sidemenu/viewmodels/SideMenuViewModel.kt
@@ -54,7 +54,7 @@ class SideMenuViewModel : ViewModel() {
             core: Core,
             cfg: ProxyConfig,
             state: RegistrationState,
-            message: String?
+            message: String
         ) {
             if (coreContext.core.proxyConfigList.size != accounts.value?.size) {
                 // Only refresh the list if a proxy has been added or removed
diff --git a/app/src/main/java/org/linphone/notifications/NotificationsManager.kt b/app/src/main/java/org/linphone/notifications/NotificationsManager.kt
index 6fa963889..bcbae6138 100644
--- a/app/src/main/java/org/linphone/notifications/NotificationsManager.kt
+++ b/app/src/main/java/org/linphone/notifications/NotificationsManager.kt
@@ -110,10 +110,10 @@ class NotificationsManager(private val context: Context) {
 
     private val listener: CoreListenerStub = object : CoreListenerStub() {
         override fun onCallStateChanged(
-            core: Core?,
-            call: Call?,
-            state: Call.State?,
-            message: String?
+            core: Core,
+            call: Call,
+            state: Call.State,
+            message: String
         ) {
             if (call == null) return
             Log.i("[Notifications Manager] Call state changed [$state]")