diff --git a/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectReason.cs b/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectReason.cs
index 3e1bb661..e1ea30d7 100644
--- a/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectReason.cs
+++ b/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectReason.cs
@@ -3,6 +3,34 @@
     public enum MqttClientDisconnectReason
     {
         NormalDisconnection = 0,
-
+        DisconnectWithWillMessage = 4,
+        UnspecifiedError = 128,
+        MalformedPacket = 129,
+        ProtocolError = 130,
+        ImplementationSpecificError = 131,
+        NotAuthorized = 135,
+        ServerBusy = 137,
+        ServerShuttingDown = 139,
+        BadAuthenticationMethod = 140,
+        KeepaliveTimeout = 141,
+        SessionTakenOver = 142,
+        TopicFilterInvalid = 143,
+        TopicNameInvalid = 144,
+        ReceiveMaximumExceeded = 147,
+        TopicAliasInvalid = 148,
+        PacketTooLarge = 149,
+        MessageRateTooHigh = 150,
+        QuotaExceeded = 151,
+        AdministrativeAction = 152,
+        PayloadFormatInvalid = 153,
+        RetainNotSupported = 154,
+        QosNotSupported = 155,
+        UseAnotherServer = 156,
+        ServerMoved = 157,
+        SharedSubscriptionsNotSupported = 158,
+        ConnectionRateExceeded = 159,
+        MaximumConnectTime = 160,
+        SubscriptionIdentifiersNotSupported = 161,
+        WildcardSubscriptionsNotSupported = 162
     }
 }
diff --git a/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs b/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs
index 7658e157..24b45345 100644
--- a/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs
+++ b/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs
@@ -5,11 +5,12 @@ namespace MQTTnet.Client.Disconnecting
 {
     public class MqttClientDisconnectedEventArgs : EventArgs
     {
-        public MqttClientDisconnectedEventArgs(bool clientWasConnected, Exception exception, MqttClientAuthenticateResult authenticateResult)
+        public MqttClientDisconnectedEventArgs(bool clientWasConnected, Exception exception, MqttClientAuthenticateResult authenticateResult, MqttClientDisconnectReason reasonCode)
         {
             ClientWasConnected = clientWasConnected;
             Exception = exception;
             AuthenticateResult = authenticateResult;
+            ReasonCode = reasonCode;
         }
 
         public bool ClientWasConnected { get; }
@@ -17,5 +18,7 @@ namespace MQTTnet.Client.Disconnecting
         public Exception Exception { get; }
 
         public MqttClientAuthenticateResult AuthenticateResult { get; }
+
+        public MqttClientDisconnectReason ReasonCode { get; set; } = MqttClientDisconnectReason.NormalDisconnection;
     }
 }
diff --git a/Source/MQTTnet/Client/MqttClient.cs b/Source/MQTTnet/Client/MqttClient.cs
index 5be12034..c80dd547 100644
--- a/Source/MQTTnet/Client/MqttClient.cs
+++ b/Source/MQTTnet/Client/MqttClient.cs
@@ -303,6 +303,7 @@ namespace MQTTnet.Client
         async Task DisconnectInternalAsync(Task sender, Exception exception, MqttClientAuthenticateResult authenticateResult)
         {
             var clientWasConnected = IsConnected;
+            var reasonCode = MqttClientDisconnectReason.NormalDisconnection;
 
             TryInitiateDisconnect();
             _isConnected = false;
@@ -320,6 +321,7 @@ namespace MQTTnet.Client
             catch (Exception adapterException)
             {
                 _logger.Warning(adapterException, "Error while disconnecting from adapter.");
+                reasonCode = MqttClientDisconnectReason.UnspecifiedError;
             }
 
             try
@@ -335,6 +337,7 @@ namespace MQTTnet.Client
             catch (Exception e)
             {
                 _logger.Warning(e, "Error while waiting for internal tasks.");
+                reasonCode = MqttClientDisconnectReason.UnspecifiedError;
             }
             finally
             {
@@ -348,7 +351,7 @@ namespace MQTTnet.Client
                 {
                     // This handler must be executed in a new thread because otherwise a dead lock may happen
                     // when trying to reconnect in that handler etc.
-                    Task.Run(() => disconnectedHandler.HandleDisconnectedAsync(new MqttClientDisconnectedEventArgs(clientWasConnected, exception, authenticateResult))).Forget(_logger);
+                    Task.Run(() => disconnectedHandler.HandleDisconnectedAsync(new MqttClientDisconnectedEventArgs(clientWasConnected, exception, authenticateResult, reasonCode))).Forget(_logger);
                 }
             }
         }