diff --git a/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs b/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs
index 24b45345..5e2317cf 100644
--- a/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs
+++ b/Source/MQTTnet/Client/Disconnecting/MqttClientDisconnectedEventArgs.cs
@@ -3,14 +3,16 @@ using MQTTnet.Client.Connecting;
 
 namespace MQTTnet.Client.Disconnecting
 {
-    public class MqttClientDisconnectedEventArgs : EventArgs
+    public sealed class MqttClientDisconnectedEventArgs : EventArgs
     {
-        public MqttClientDisconnectedEventArgs(bool clientWasConnected, Exception exception, MqttClientAuthenticateResult authenticateResult, MqttClientDisconnectReason reasonCode)
+        public MqttClientDisconnectedEventArgs(bool clientWasConnected, Exception exception, MqttClientAuthenticateResult authenticateResult, MqttClientDisconnectReason reason)
         {
             ClientWasConnected = clientWasConnected;
             Exception = exception;
             AuthenticateResult = authenticateResult;
-            ReasonCode = reasonCode;
+            Reason = reason;
+
+            ReasonCode = reason;
         }
 
         public bool ClientWasConnected { get; }
@@ -19,6 +21,9 @@ namespace MQTTnet.Client.Disconnecting
 
         public MqttClientAuthenticateResult AuthenticateResult { get; }
 
-        public MqttClientDisconnectReason ReasonCode { get; set; } = MqttClientDisconnectReason.NormalDisconnection;
+        public MqttClientDisconnectReason Reason { get; set; }
+
+        [Obsolete("Please use 'Reason' instead. This property will be removed in the future!")]
+        public MqttClientDisconnectReason ReasonCode { get; set; }
     }
 }
diff --git a/Tests/MQTTnet.Core.Tests/Server_Tests.cs b/Tests/MQTTnet.Core.Tests/Server_Tests.cs
index 71c819d1..4c00af6a 100644
--- a/Tests/MQTTnet.Core.Tests/Server_Tests.cs
+++ b/Tests/MQTTnet.Core.Tests/Server_Tests.cs
@@ -471,11 +471,19 @@ namespace MQTTnet.Tests
                 var client1 = await testEnvironment.ConnectClientAsync(options);
                 await Task.Delay(500);
 
+                MqttClientDisconnectReason disconnectReason = MqttClientDisconnectReason.NormalDisconnection;
+                client1.DisconnectedHandler = new MqttClientDisconnectedHandlerDelegate(c =>
+                {
+                    disconnectReason = c.Reason;
+                });
+
                 var client2 = await testEnvironment.ConnectClientAsync(options);
                 await Task.Delay(500);
 
                 Assert.IsFalse(client1.IsConnected);
                 Assert.IsTrue(client2.IsConnected);
+
+                Assert.AreEqual(MqttClientDisconnectReason.SessionTakenOver, disconnectReason);
             }
         }