diff --git a/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs b/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs
index 6dec29f..271e6b9 100644
--- a/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs
+++ b/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClient.cs
@@ -113,7 +113,7 @@ namespace MQTTnet.Extensions.ManagedClient
         {
             if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
 
-            ManagedMqttApplicationMessage skippedMessage = null;
+            ManagedMqttApplicationMessage removedMessage = null;
             lock (_messageQueue)
             {
                 if (_messageQueue.Count >= _options.MaxPendingMessages)
@@ -127,9 +127,9 @@ namespace MQTTnet.Extensions.ManagedClient
 
                     if (_options.PendingMessagesOverflowStrategy == MqttPendingMessagesOverflowStrategy.DropOldestQueuedMessage)
                     {
-                        skippedMessage = _messageQueue.RemoveFirst();
+                        removedMessage = _messageQueue.RemoveFirst();
                         _logger.Verbose("Removed oldest application message from internal queue because it is full.");
-                        ApplicationMessageSkipped?.Invoke(this, new ApplicationMessageSkippedEventArgs(skippedMessage));
+                        ApplicationMessageSkipped?.Invoke(this, new ApplicationMessageSkippedEventArgs(removedMessage));
                     }
                 }
 
@@ -138,9 +138,9 @@ namespace MQTTnet.Extensions.ManagedClient
 
             if (_storageManager != null)
             {
-                if (skippedMessage != null)
+                if (removedMessage != null)
                 {
-                    await _storageManager.RemoveAsync(skippedMessage).ConfigureAwait(false);
+                    await _storageManager.RemoveAsync(removedMessage).ConfigureAwait(false);
                 }
 
                 await _storageManager.AddAsync(applicationMessage).ConfigureAwait(false);
diff --git a/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClientStorageManager.cs b/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClientStorageManager.cs
index 0f4e33e..821a7d9 100644
--- a/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClientStorageManager.cs
+++ b/Source/MQTTnet.Extensions.ManagedClient/ManagedMqttClientStorageManager.cs
@@ -28,6 +28,8 @@ namespace MQTTnet.Extensions.ManagedClient
 
         public async Task AddAsync(ManagedMqttApplicationMessage applicationMessage)
         {
+            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
+
             using (await _messagesLock.LockAsync(CancellationToken.None).ConfigureAwait(false))
             {
                 _messages.Add(applicationMessage);
@@ -37,6 +39,8 @@ namespace MQTTnet.Extensions.ManagedClient
 
         public async Task RemoveAsync(ManagedMqttApplicationMessage applicationMessage)
         {
+            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));
+
             using (await _messagesLock.LockAsync(CancellationToken.None).ConfigureAwait(false))
             {
                 var index = _messages.IndexOf(applicationMessage);
diff --git a/Source/MQTTnet/Internal/BlockingQueue.cs b/Source/MQTTnet/Internal/BlockingQueue.cs
index ae6cc98..d6c28f4 100644
--- a/Source/MQTTnet/Internal/BlockingQueue.cs
+++ b/Source/MQTTnet/Internal/BlockingQueue.cs
@@ -62,6 +62,7 @@ namespace MQTTnet.Internal
             {
                 var item = _items.First;
                 _items.RemoveFirst();
+
                 return item.Value;
             }
         }