diff --git a/Source/MQTTnet/Server/MqttClientSession.cs b/Source/MQTTnet/Server/MqttClientSession.cs
index 70b04d9..f318b85 100644
--- a/Source/MQTTnet/Server/MqttClientSession.cs
+++ b/Source/MQTTnet/Server/MqttClientSession.cs
@@ -11,12 +11,13 @@ namespace MQTTnet.Server
         readonly IMqttNetLogger _logger;
 
         readonly DateTime _createdTimestamp = DateTime.UtcNow;
+        readonly IMqttRetainedMessagesManager _retainedMessagesManager;
 
-        public MqttClientSession(string clientId, IDictionary<object, object> items, MqttServerEventDispatcher eventDispatcher, IMqttServerOptions serverOptions, IMqttNetLogger logger)
+        public MqttClientSession(string clientId, IDictionary<object, object> items, MqttServerEventDispatcher eventDispatcher, IMqttServerOptions serverOptions, IMqttRetainedMessagesManager retainedMessagesManager, IMqttNetLogger logger)
         {
             ClientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
             Items = items ?? throw new ArgumentNullException(nameof(items));
-
+            _retainedMessagesManager = retainedMessagesManager ?? throw new ArgumentNullException(nameof(retainedMessagesManager));
             SubscriptionsManager = new MqttClientSubscriptionsManager(this, eventDispatcher, serverOptions);
             ApplicationMessagesQueue = new MqttClientSessionApplicationMessagesQueue(serverOptions);
 
@@ -52,11 +53,13 @@ namespace MQTTnet.Server
             ApplicationMessagesQueue.Enqueue(applicationMessage, senderClientId, checkSubscriptionsResult.QualityOfServiceLevel, isRetainedApplicationMessage);
         }
 
-        public async Task SubscribeAsync(ICollection<TopicFilter> topicFilters, IMqttRetainedMessagesManager retainedMessagesManager)
+        public async Task SubscribeAsync(ICollection<TopicFilter> topicFilters)
         {
+            if (topicFilters is null) throw new ArgumentNullException(nameof(topicFilters));
+
             await SubscriptionsManager.SubscribeAsync(topicFilters).ConfigureAwait(false);
 
-            var matchingRetainedMessages = await retainedMessagesManager.GetSubscribedMessagesAsync(topicFilters).ConfigureAwait(false);
+            var matchingRetainedMessages = await _retainedMessagesManager.GetSubscribedMessagesAsync(topicFilters).ConfigureAwait(false);
             foreach (var matchingRetainedMessage in matchingRetainedMessages)
             {
                 EnqueueApplicationMessage(matchingRetainedMessage, null, true);
@@ -65,6 +68,8 @@ namespace MQTTnet.Server
 
         public Task UnsubscribeAsync(IEnumerable<string> topicFilters)
         {
+            if (topicFilters is null) throw new ArgumentNullException(nameof(topicFilters));
+
             return SubscriptionsManager.UnsubscribeAsync(topicFilters);
         }
 
diff --git a/Source/MQTTnet/Server/MqttClientSessionsManager.cs b/Source/MQTTnet/Server/MqttClientSessionsManager.cs
index f98eb05..b10f8f7 100644
--- a/Source/MQTTnet/Server/MqttClientSessionsManager.cs
+++ b/Source/MQTTnet/Server/MqttClientSessionsManager.cs
@@ -118,7 +118,7 @@ namespace MQTTnet.Server
                 throw new InvalidOperationException($"Client session '{clientId}' is unknown.");
             }
 
-            return session.SubscribeAsync(topicFilters, _retainedMessagesManager);
+            return session.SubscribeAsync(topicFilters);
         }
 
         public Task UnsubscribeAsync(string clientId, IEnumerable<string> topicFilters)
@@ -280,7 +280,7 @@ namespace MQTTnet.Server
                     connectPacket,
                     connectionValidatorContext,
                     channelAdapter,
-                    async () => await _eventDispatcher.SafeNotifyClientConnectedAsync(clientId).ConfigureAwait(false), 
+                    async () => await _eventDispatcher.SafeNotifyClientConnectedAsync(clientId).ConfigureAwait(false),
                     async disconnectType => await CleanUpClient(clientId, channelAdapter, disconnectType)
                 ).ConfigureAwait(false);
 
@@ -371,7 +371,7 @@ namespace MQTTnet.Server
 
                 if (session == null)
                 {
-                    session = new MqttClientSession(connectPacket.ClientId, connectionValidatorContext.SessionItems, _eventDispatcher, _options, _logger);
+                    session = new MqttClientSession(connectPacket.ClientId, connectionValidatorContext.SessionItems, _eventDispatcher, _options, _retainedMessagesManager, _logger);
                     _logger.Verbose("Created a new session for client '{0}'.", connectPacket.ClientId);
                 }
 
diff --git a/Tests/MQTTnet.Core.Tests/MqttSubscriptionsManager_Tests.cs b/Tests/MQTTnet.Core.Tests/MqttSubscriptionsManager_Tests.cs
index 6f0d542..3c7724d 100644
--- a/Tests/MQTTnet.Core.Tests/MqttSubscriptionsManager_Tests.cs
+++ b/Tests/MQTTnet.Core.Tests/MqttSubscriptionsManager_Tests.cs
@@ -1,10 +1,10 @@
-using System.Collections.Concurrent;
-using System.Threading.Tasks;
-using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
 using MQTTnet.Server;
 using MQTTnet.Tests.Mockups;
+using System.Collections.Concurrent;
+using System.Threading.Tasks;
 
 namespace MQTTnet.Tests
 {
@@ -14,8 +14,7 @@ namespace MQTTnet.Tests
         [TestMethod]
         public async Task MqttSubscriptionsManager_SubscribeSingleSuccess()
         {
-            var s = new MqttClientSession("", new ConcurrentDictionary<object, object>(),
-                new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions(), new TestLogger());
+            var s = CreateSession();
 
             var sm = new MqttClientSubscriptionsManager(s, new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions());
 
@@ -32,8 +31,7 @@ namespace MQTTnet.Tests
         [TestMethod]
         public async Task MqttSubscriptionsManager_SubscribeDifferentQoSSuccess()
         {
-            var s = new MqttClientSession("", new ConcurrentDictionary<object, object>(),
-                new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions(), new TestLogger());
+            var s = CreateSession();
 
             var sm = new MqttClientSubscriptionsManager(s, new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions());
 
@@ -50,8 +48,7 @@ namespace MQTTnet.Tests
         [TestMethod]
         public async Task MqttSubscriptionsManager_SubscribeTwoTimesSuccess()
         {
-            var s = new MqttClientSession("", new ConcurrentDictionary<object, object>(),
-                new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions(), new TestLogger());
+            var s = CreateSession();
 
             var sm = new MqttClientSubscriptionsManager(s, new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions());
 
@@ -69,8 +66,7 @@ namespace MQTTnet.Tests
         [TestMethod]
         public async Task MqttSubscriptionsManager_SubscribeSingleNoSuccess()
         {
-            var s = new MqttClientSession("", new ConcurrentDictionary<object, object>(),
-                new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions(), new TestLogger());
+            var s = CreateSession();
 
             var sm = new MqttClientSubscriptionsManager(s, new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions());
 
@@ -85,8 +81,7 @@ namespace MQTTnet.Tests
         [TestMethod]
         public async Task MqttSubscriptionsManager_SubscribeAndUnsubscribeSingle()
         {
-            var s = new MqttClientSession("", new ConcurrentDictionary<object, object>(),
-                new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions(), new TestLogger());
+            var s = CreateSession();
 
             var sm = new MqttClientSubscriptionsManager(s, new MqttServerEventDispatcher(new TestLogger()), new MqttServerOptions());
 
@@ -103,5 +98,16 @@ namespace MQTTnet.Tests
 
             Assert.IsFalse(sm.CheckSubscriptions("A/B/C", MqttQualityOfServiceLevel.AtMostOnce).IsSubscribed);
         }
+
+        MqttClientSession CreateSession()
+        {
+            return new MqttClientSession(
+                "",
+                new ConcurrentDictionary<object, object>(),
+                new MqttServerEventDispatcher(new TestLogger()),
+                new MqttServerOptions(),
+                new MqttRetainedMessagesManager(),
+                new TestLogger());
+        }
     }
 }