diff --git a/lib/src/logger.dart b/lib/src/logger.dart
index 43af3092..a1a107c6 100644
--- a/lib/src/logger.dart
+++ b/lib/src/logger.dart
@@ -130,7 +130,7 @@ class AnsiColor {
 
   String call(String msg) {
     if (color) {
-      return '${this}$msg$ansiDefault';
+      return '$this$msg$ansiDefault';
     } else {
       return msg;
     }
diff --git a/lib/src/rtc_session.dart b/lib/src/rtc_session.dart
index 05a48a7d..09de6c9f 100644
--- a/lib/src/rtc_session.dart
+++ b/lib/src/rtc_session.dart
@@ -2701,14 +2701,14 @@ class RTCSession extends EventManager implements Owner {
    * Correctly set the SDP direction attributes if the call is on local hold
    */
   String? _mangleOffer(String? sdpInput) {
-    if (!_localHold! && !_remoteHold!) {
+    if (!_localHold && !_remoteHold) {
       return sdpInput;
     }
 
     Map<String, dynamic> sdp = sdp_transform.parse(sdpInput!);
 
     // Local hold.
-    if (_localHold! && !_remoteHold!) {
+    if (_localHold && !_remoteHold) {
       logger.d('mangleOffer() | me on hold, mangling offer');
       for (Map<String, dynamic> m in sdp['media']) {
         if (holdMediaTypes.indexOf(m['type']) == -1) {
@@ -2724,7 +2724,7 @@ class RTCSession extends EventManager implements Owner {
       }
     }
     // Local and remote hold.
-    else if (_localHold! && _remoteHold!) {
+    else if (_localHold && _remoteHold) {
       logger.d('mangleOffer() | both on hold, mangling offer');
       for (Map<String, dynamic> m in sdp['media']) {
         if (holdMediaTypes.indexOf(m['type']) == -1) {
@@ -2734,7 +2734,7 @@ class RTCSession extends EventManager implements Owner {
       }
     }
     // Remote hold.
-    else if (_remoteHold!) {
+    else if (_remoteHold) {
       logger.d('mangleOffer() | remote on hold, mangling offer');
       for (Map<String, dynamic> m in sdp['media']) {
         if (holdMediaTypes.indexOf(m['type']) == -1) {
@@ -2756,16 +2756,16 @@ class RTCSession extends EventManager implements Owner {
   void _setLocalMediaStatus() {
     bool enableAudio = true, enableVideo = true;
 
-    if (_localHold! || _remoteHold!) {
+    if (_localHold || _remoteHold) {
       enableAudio = false;
       enableVideo = false;
     }
 
-    if (_audioMuted!) {
+    if (_audioMuted) {
       enableAudio = false;
     }
 
-    if (_videoMuted!) {
+    if (_videoMuted) {
       enableVideo = false;
     }
 
diff --git a/lib/src/sip_ua_helper.dart b/lib/src/sip_ua_helper.dart
index d4856d0e..4403939c 100644
--- a/lib/src/sip_ua_helper.dart
+++ b/lib/src/sip_ua_helper.dart
@@ -371,7 +371,7 @@ class SIPUAHelper extends EventManager {
 
   void _notifyTransportStateListeners(TransportState state) {
     // Copy to prevent concurrent modification exception
-    var _listeners = _sipUaHelperListeners.toList();
+    List<SipUaHelperListener> _listeners = _sipUaHelperListeners.toList();
     for (SipUaHelperListener listener in _listeners) {
       listener.transportStateChanged(state);
     }
@@ -379,7 +379,7 @@ class SIPUAHelper extends EventManager {
 
   void _notifyRegistrationStateListeners(RegistrationState state) {
     // Copy to prevent concurrent modification exception
-    var _listeners = _sipUaHelperListeners.toList();
+    List<SipUaHelperListener> _listeners = _sipUaHelperListeners.toList();
     for (SipUaHelperListener listener in _listeners) {
       listener.registrationStateChanged(state);
     }
@@ -393,7 +393,7 @@ class SIPUAHelper extends EventManager {
     }
     call.state = state.state;
     // Copy to prevent concurrent modification exception
-    var _listeners = _sipUaHelperListeners.toList();
+    List<SipUaHelperListener> _listeners = _sipUaHelperListeners.toList();
     for (SipUaHelperListener listener in _listeners) {
       listener.callStateChanged(call, state);
     }
@@ -401,7 +401,7 @@ class SIPUAHelper extends EventManager {
 
   void _notifyNewMessageListeners(SIPMessageRequest msg) {
     // Copy to prevent concurrent modification exception
-    var _listeners = _sipUaHelperListeners.toList();
+    List<SipUaHelperListener> _listeners = _sipUaHelperListeners.toList();
     for (SipUaHelperListener listener in _listeners) {
       listener.onNewMessage(msg);
     }
@@ -409,7 +409,7 @@ class SIPUAHelper extends EventManager {
 
   void _notifyNotifyListeners(EventNotify event) {
     // Copy to prevent concurrent modification exception
-    var _listeners = _sipUaHelperListeners.toList();
+    List<SipUaHelperListener> _listeners = _sipUaHelperListeners.toList();
     for (SipUaHelperListener listener in _listeners) {
       listener.onNewNotify(Notify(request: event.request));
     }
diff --git a/lib/src/transports/websocket_interface.dart b/lib/src/transports/websocket_interface.dart
index 99e2af77..36651612 100644
--- a/lib/src/transports/websocket_interface.dart
+++ b/lib/src/transports/websocket_interface.dart
@@ -7,8 +7,6 @@ import 'websocket_dart_impl.dart'
     if (dart.library.js) 'websocket_web_impl.dart';
 
 class WebSocketInterface implements Socket {
-  final int _messageDelay;
-
   WebSocketInterface(String url,
       {required int messageDelay, WebSocketSettings? webSocketSettings})
       : _messageDelay = messageDelay {
@@ -34,6 +32,7 @@ class WebSocketInterface implements Socket {
     }
     _webSocketSettings = webSocketSettings ?? WebSocketSettings();
   }
+  final int _messageDelay;
 
   String? _url;
   String? _sip_uri;
diff --git a/test/all_test.dart b/test/all_test.dart
index 20d39099..7667228e 100644
--- a/test/all_test.dart
+++ b/test/all_test.dart
@@ -17,7 +17,7 @@ void main() {
   for (Function func in DigestAuthentication.testFunctions) {
     func();
   }
-  for (Function func in Websocket.testFunctions) {
-    //func();
-  }
+  //for (Function _func in Websocket.testFunctions) {
+  //func();
+  //}
 }