diff --git a/Source/MQTTnet/Server/MqttClientSessionsManager.cs b/Source/MQTTnet/Server/MqttClientSessionsManager.cs
index 400045b4..8bc800ea 100644
--- a/Source/MQTTnet/Server/MqttClientSessionsManager.cs
+++ b/Source/MQTTnet/Server/MqttClientSessionsManager.cs
@@ -62,7 +62,7 @@ namespace MQTTnet.Server
 
         public Task StartSession(IMqttChannelAdapter clientAdapter)
         {
-            return Task.Run(() => RunSession(clientAdapter, _cancellationToken), _cancellationToken);
+            return Task.Run(() => RunSessionAsync(clientAdapter, _cancellationToken), _cancellationToken);
         }
 
         public IList<IMqttClientSessionStatus> GetClientStatus()
@@ -205,7 +205,7 @@ namespace MQTTnet.Server
             }
         }
 
-        private async Task RunSession(IMqttChannelAdapter clientAdapter, CancellationToken cancellationToken)
+        private async Task RunSessionAsync(IMqttChannelAdapter clientAdapter, CancellationToken cancellationToken)
         {
             var clientId = string.Empty;
             
@@ -241,7 +241,8 @@ namespace MQTTnet.Server
                 }
 
                 var result = PrepareClientSession(connectPacket);
-                var clientSession = result.Session;
+
+                Server.OnClientConnected(clientId);
 
                 await clientAdapter.SendPacketAsync(
                     new MqttConnAckPacket
@@ -251,9 +252,7 @@ namespace MQTTnet.Server
                     },
                     cancellationToken).ConfigureAwait(false);
 
-                Server.OnClientConnected(clientId);
-
-                await clientSession.RunAsync(connectPacket, clientAdapter).ConfigureAwait(false);
+                await result.Session.RunAsync(connectPacket, clientAdapter).ConfigureAwait(false);
             }
             catch (OperationCanceledException)
             {
diff --git a/Tests/MQTTnet.Core.Tests/MqttServerTests.cs b/Tests/MQTTnet.Core.Tests/MqttServerTests.cs
index 4836f4de..2a48e993 100644
--- a/Tests/MQTTnet.Core.Tests/MqttServerTests.cs
+++ b/Tests/MQTTnet.Core.Tests/MqttServerTests.cs
@@ -660,16 +660,22 @@ namespace MQTTnet.Core.Tests
         {
             var s = new MqttFactory().CreateMqttServer();
 
-            var events = new ConcurrentBag<string>();
+            var events = new List<string>();
 
             s.ClientConnected += (_, __) =>
             {
-                events.Add("c");
+                lock (events)
+                {
+                    events.Add("c");
+                }
             };
 
             s.ClientDisconnected += (_, __) =>
             {
-                events.Add("d");
+                lock (events)
+                {
+                    events.Add("d");
+                }
             };
 
             var clientOptions = new MqttClientOptionsBuilder()
@@ -691,17 +697,17 @@ namespace MQTTnet.Core.Tests
             await Task.Delay(250);
 
             await c1.DisconnectAsync();
+
+            await Task.Delay(250);
+
             await c2.DisconnectAsync();
 
             await Task.Delay(250);
 
-            var flow = string.Join(string.Empty, events);
-            
             await s.StopAsync();
 
+            var flow = string.Join(string.Empty, events);
             Assert.AreEqual("cdcd", flow);
-
-            //Assert.IsFalse(connecteCalledBeforeConnectedClients, "ClientConnected was called before ClientDisconnect was called");
         }