diff --git a/call_sample/android/app/proguard-rules.pro b/call_sample/android/app/proguard-rules.pro
index 07cef8f..b48f077 100644
--- a/call_sample/android/app/proguard-rules.pro
+++ b/call_sample/android/app/proguard-rules.pro
@@ -1,4 +1,15 @@
 #Flutter Wrapper
--dontwarn org.webrtc.**
+# WebRTC
 -keep class org.webrtc.** { *; }
+-dontwarn org.webrtc.**
+-keepclassmembers class org.webrtc.** { *; }
+
+# JNI
+-keepclasseswithmembernames class * {
+    native <methods>;
+}
+-keep class org.jni_zero.** { *; }
+
+# Stringee
+-dontwarn com.stringee.**
 -keep class com.stringee.** { *; }
diff --git a/call_sample/lib/stringee_wrapper/call/stringee_call_model.dart b/call_sample/lib/stringee_wrapper/call/stringee_call_model.dart
index ff7f057..ed1afe0 100644
--- a/call_sample/lib/stringee_wrapper/call/stringee_call_model.dart
+++ b/call_sample/lib/stringee_wrapper/call/stringee_call_model.dart
@@ -175,7 +175,7 @@ class StringeeCallModel extends ChangeNotifier {
     });
   }
 
-  _handleStringeeCallEvent(Map<dynamic, dynamic> event) async {
+  Future<void> _handleStringeeCallEvent(Map<dynamic, dynamic> event) async {
     switch (event['eventType']) {
       /// StringeeCallEvents
       case StringeeCallEvents.didChangeSignalingState:
@@ -491,7 +491,7 @@ class StringeeCallModel extends ChangeNotifier {
     return Response.success('Call answered already');
   }
 
-  startTimerIfNeeded() {
+  void startTimerIfNeeded() {
     if (!_startedTimer) {
       _startedTimer = true;
       _time = '00:00';
diff --git a/call_sample/pubspec.yaml b/call_sample/pubspec.yaml
index fc81356..d03b6c9 100644
--- a/call_sample/pubspec.yaml
+++ b/call_sample/pubspec.yaml
@@ -13,7 +13,7 @@ dependencies:
 
   cupertino_icons: 1.0.8
 
-  stringee_plugin: ^1.2.14
+  stringee_plugin: ^1.2.16
 
   #for ios
   uuid: ^4.5.1