diff --git a/android/build.gradle b/android/build.gradle
index 64e247dc..59f9560b 100644
--- a/android/build.gradle
+++ b/android/build.gradle
@@ -23,10 +23,10 @@ rootProject.allprojects {
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion 28
+    compileSdkVersion 33
 
     defaultConfig {
-        minSdkVersion 18
+        minSdkVersion 21
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
     lintOptions {
diff --git a/lib/src/bridge/characteristics_mixin.dart b/lib/src/bridge/characteristics_mixin.dart
index 12a80d52..05158c7a 100644
--- a/lib/src/bridge/characteristics_mixin.dart
+++ b/lib/src/bridge/characteristics_mixin.dart
@@ -26,9 +26,8 @@ mixin CharacteristicsMixin on FlutterBLE {
               rawJsonValue = rawValue;
             }
             return _parseCharacteristicWithValueWithTransactionIdResponse(
-              peripheral, 
-              rawJsonValue
-            ).value;
+                    peripheral, rawJsonValue)
+                .value;
           });
 
   Future<CharacteristicWithValue> readCharacteristicForDevice(
@@ -55,9 +54,7 @@ mixin CharacteristicsMixin on FlutterBLE {
               rawJsonValue = rawValue;
             }
             return _parseCharacteristicWithValueWithTransactionIdResponse(
-              peripheral, 
-              rawJsonValue
-            );
+                peripheral, rawJsonValue);
           });
 
   Future<CharacteristicWithValue> readCharacteristicForService(
@@ -83,9 +80,7 @@ mixin CharacteristicsMixin on FlutterBLE {
               rawJsonValue = rawValue;
             }
             return _parseCharacteristicWithValueWithTransactionIdResponse(
-              peripheral, 
-              rawJsonValue
-            );
+                peripheral, rawJsonValue);
           });
 
   Future<void> writeCharacteristicForIdentifier(
@@ -181,7 +176,9 @@ mixin CharacteristicsMixin on FlutterBLE {
         transactionId,
         characteristic._transactionId ?? "",
       );
-    };
+    }
+
+    ;
 
     return _createMonitoringStream(
       startMonitoring,
@@ -259,23 +256,20 @@ mixin CharacteristicsMixin on FlutterBLE {
     String transactionId,
   ) {
     Stream<CharacteristicWithValueAndTransactionId> stream =
-      _characteristicsMonitoringEvents
-        .map((rawValue) {
-          String rawJsonValue = "";
-          if (rawValue is String) {
-            rawJsonValue = rawValue;
-          }
-          return _parseCharacteristicWithValueWithTransactionIdResponse(
-            peripheral, 
-            rawJsonValue
-          );
-        })
-        .where(filter)
-        .handleError((errorJson) =>
-            _throwErrorIfMatchesWithTransactionId(errorJson, transactionId))
-        .transform<CharacteristicWithValueAndTransactionId>(
-          CancelOnErrorStreamTransformer()
-        );
+        _characteristicsMonitoringEvents
+            .map((rawValue) {
+              String rawJsonValue = "";
+              if (rawValue is String) {
+                rawJsonValue = rawValue;
+              }
+              return _parseCharacteristicWithValueWithTransactionIdResponse(
+                  peripheral, rawJsonValue);
+            })
+            .where(filter)
+            .handleError((errorJson) =>
+                _throwErrorIfMatchesWithTransactionId(errorJson, transactionId))
+            .transform<CharacteristicWithValueAndTransactionId>(
+                CancelOnErrorStreamTransformer());
 
     StreamController<CharacteristicWithValueAndTransactionId> streamController =
         StreamController.broadcast(
@@ -311,7 +305,8 @@ mixin CharacteristicsMixin on FlutterBLE {
         rootObject["characteristic"], service, _manager);
   }
 
-  void _throwErrorIfMatchesWithTransactionId(PlatformException errorJson, String transactionId) {
+  void _throwErrorIfMatchesWithTransactionId(
+      PlatformException errorJson, String transactionId) {
     if (errorJson is PlatformException == false) {
       return;
     }
@@ -333,7 +328,8 @@ class CharacteristicWithValueAndTransactionId extends CharacteristicWithValue {
   ) : super.fromJson(jsonObject, service, manager);
 
   CharacteristicWithValueAndTransactionId setTransactionId(
-      String transactionId) {
+    String? transactionId,
+  ) {
     _transactionId = transactionId;
     return this;
   }
diff --git a/pubspec.yaml b/pubspec.yaml
index 08664996..107c5459 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -4,7 +4,7 @@ version: 2.4.0
 homepage: https://github.com/Polidea/FlutterBleLib
 
 environment:
-  sdk: ">=2.12.0-0 <3.0.0"
+  sdk: ">=3.1.0 <4.0.0"
   # Flutter versions prior to 1.10 did not support the flutter.plugin.platforms map.
   flutter: ">=1.10.0 <2.0.0"
 
@@ -16,7 +16,7 @@ dependencies:
 
 dev_dependencies:
   mockito: ^5.0.3
-  build_runner: ^1.12.2
+  build_runner: ^2.4.6
   pedantic: ^1.11.0
 
   flutter_test: