diff --git a/lib/aptabase_flutter.dart b/lib/aptabase_flutter.dart
index 795ae36..380007d 100644
--- a/lib/aptabase_flutter.dart
+++ b/lib/aptabase_flutter.dart
@@ -27,7 +27,7 @@ enum _SendResult { disabled, success, discard, tryAgain }
 class Aptabase {
   Aptabase._();
 
-  static const _sdkVersion = "aptabase_flutter@0.4.1";
+  static const _sdkVersion = "aptabase_flutter@0.4.2";
   static const _sessionTimeout = Duration(hours: 1);
 
   static const Map<String, String> _hosts = {
@@ -39,9 +39,9 @@ class Aptabase {
 
   static final _http = newUniversalHttpClient();
 
-  static late final String _appKey;
+  static String? _appKey;
+  static Uri? _apiUrl;
   static late final InitOptions _initOptions;
-  static late final Uri? _apiUrl;
   static var _sessionId = _newSessionId();
   static var _lastTouchTs = DateTime.now().toUtc();
   static Timer? _timer;
@@ -187,7 +187,8 @@ class Aptabase {
     String eventName, [
     Map<String, dynamic>? props,
   ]) async {
-    if (_appKey.isEmpty || _apiUrl == null) {
+    final appKey = _appKey;
+    if (_apiUrl == null || appKey == null || appKey.isEmpty) {
       _logInfo("Tracking is disabled!");
 
       return;
@@ -211,7 +212,8 @@ class Aptabase {
   static Future<_SendResult> _send(List<String> events) async {
     try {
       final apiUrl = _apiUrl;
-      if (apiUrl == null) {
+      final appKey = _appKey;
+      if (apiUrl == null || appKey == null) {
         _logInfo("Tracking is disabled!");
 
         return _SendResult.disabled;
@@ -221,7 +223,7 @@ class Aptabase {
 
       request.followRedirects = true;
       request.headers
-        ..set("App-Key", _appKey)
+        ..set("App-Key", appKey)
         ..set(
           HttpHeaders.contentTypeHeader,
           "application/json; charset=UTF-8",
diff --git a/pubspec.yaml b/pubspec.yaml
index 895ee98..8d15b44 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: aptabase_flutter
 description: "Flutter SDK for Aptabase: Open Source Privacy-First and Simple Analytics for Mobile, Desktop and Web Apps"
-version: 0.4.1
+version: 0.4.2
 homepage: https://aptabase.com
 repository: https://github.com/aptabase/aptabase_flutter
 issue_tracker: https://github.com/aptabase/aptabase_flutter/issues
@@ -12,12 +12,12 @@ environment:
 dependencies:
   flutter:
     sdk: flutter
-  package_info_plus: ^8.0.0
-  device_info_plus: ^10.1.0
-  universal_io: ^2.2.2
-  shared_preferences: ^2.3.3
+  package_info_plus: any
+  device_info_plus: any
+  universal_io: any
+  shared_preferences: any
 
 dev_dependencies:
   flutter_test:
     sdk: flutter
-  flutter_lints: ^4.0.0
+  flutter_lints: ^6.0.0