diff --git a/Build/MQTTnet.nuspec b/Build/MQTTnet.nuspec
index 2ecfc07..cd49b7f 100644
--- a/Build/MQTTnet.nuspec
+++ b/Build/MQTTnet.nuspec
@@ -12,6 +12,7 @@
     <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker).</description>
     <releaseNotes>
 * [Core] Fixed issues in MQTTv5 message encoding and decoding.
+* [Client] Added support for extended authentication exchange.
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2019</copyright>
     <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags> 
diff --git a/Source/MQTTnet/Client/ExtendedAuthenticationExchange/IMqttExtendedAuthenticationExchangeHandler.cs b/Source/MQTTnet/Client/ExtendedAuthenticationExchange/IMqttExtendedAuthenticationExchangeHandler.cs
new file mode 100644
index 0000000..8cd3542
--- /dev/null
+++ b/Source/MQTTnet/Client/ExtendedAuthenticationExchange/IMqttExtendedAuthenticationExchangeHandler.cs
@@ -0,0 +1,9 @@
+using System.Threading.Tasks;
+
+namespace MQTTnet.Client.ExtendedAuthenticationExchange
+{
+    public interface IMqttExtendedAuthenticationExchangeHandler
+    {
+        Task HandleRequestAsync(MqttExtendedAuthenticationExchangeContext context);
+    }
+}
diff --git a/Source/MQTTnet/Client/ExtendedAuthenticationExchange/MqttExtendedAuthenticationExchangeContext.cs b/Source/MQTTnet/Client/ExtendedAuthenticationExchange/MqttExtendedAuthenticationExchangeContext.cs
new file mode 100644
index 0000000..9e88f03
--- /dev/null
+++ b/Source/MQTTnet/Client/ExtendedAuthenticationExchange/MqttExtendedAuthenticationExchangeContext.cs
@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using MQTTnet.Packets;
+using MQTTnet.Protocol;
+
+namespace MQTTnet.Client.ExtendedAuthenticationExchange
+{
+    public class MqttExtendedAuthenticationExchangeContext
+    {
+        public MqttExtendedAuthenticationExchangeContext(MqttAuthPacket authPacket, IMqttClient client)
+        {
+            if (authPacket == null) throw new ArgumentNullException(nameof(authPacket));
+
+            ReasonCode = authPacket.ReasonCode;
+            ReasonString = authPacket.Properties?.ReasonString;
+            AuthenticationMethod = authPacket.Properties?.AuthenticationMethod;
+            AuthenticationData = authPacket.Properties?.AuthenticationData;
+            UserProperties = authPacket.Properties?.UserProperties;
+
+            Client = client ?? throw new ArgumentNullException(nameof(client));
+        }
+
+        public MqttAuthenticateReasonCode ReasonCode { get; }
+
+        public string ReasonString { get; }
+
+        public string AuthenticationMethod { get; }
+
+        public byte[] AuthenticationData { get; }
+
+        public List<MqttUserProperty> UserProperties { get; }
+
+        public IMqttClient Client { get; }
+    }
+}
diff --git a/Source/MQTTnet/Client/ExtendedAuthenticationExchange/MqttExtendedAuthenticationExchangeData.cs b/Source/MQTTnet/Client/ExtendedAuthenticationExchange/MqttExtendedAuthenticationExchangeData.cs
new file mode 100644
index 0000000..8a49b08
--- /dev/null
+++ b/Source/MQTTnet/Client/ExtendedAuthenticationExchange/MqttExtendedAuthenticationExchangeData.cs
@@ -0,0 +1,17 @@
+using System.Collections.Generic;
+using MQTTnet.Packets;
+using MQTTnet.Protocol;
+
+namespace MQTTnet.Client.ExtendedAuthenticationExchange
+{
+    public class MqttExtendedAuthenticationExchangeData
+    {
+        public MqttAuthenticateReasonCode ReasonCode { get; set; }
+
+        public string ReasonString { get; set; }
+
+        public byte[] AuthenticationData { get; set; }
+
+        public List<MqttUserProperty> UserProperties { get; }
+    }
+}
diff --git a/Source/MQTTnet/Client/IMqttClient.cs b/Source/MQTTnet/Client/IMqttClient.cs
index 70259cf..059f2e6 100644
--- a/Source/MQTTnet/Client/IMqttClient.cs
+++ b/Source/MQTTnet/Client/IMqttClient.cs
@@ -3,6 +3,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Client.Connecting;
 using MQTTnet.Client.Disconnecting;
+using MQTTnet.Client.ExtendedAuthenticationExchange;
 using MQTTnet.Client.Options;
 using MQTTnet.Client.Subscribing;
 using MQTTnet.Client.Unsubscribing;
@@ -21,6 +22,7 @@ namespace MQTTnet.Client
         Task<MqttClientAuthenticateResult> ConnectAsync(IMqttClientOptions options, CancellationToken cancellationToken);
         Task DisconnectAsync(MqttClientDisconnectOptions options, CancellationToken cancellationToken);
 
+        Task SendExtendedAuthenticationExchangeDataAsync(MqttExtendedAuthenticationExchangeData data, CancellationToken cancellationToken);
         Task<MqttClientSubscribeResult> SubscribeAsync(MqttClientSubscribeOptions options, CancellationToken cancellationToken);
         Task<MqttClientUnsubscribeResult> UnsubscribeAsync(MqttClientUnsubscribeOptions options, CancellationToken cancellationToken);
     }
diff --git a/Source/MQTTnet/Client/MqttClient.cs b/Source/MQTTnet/Client/MqttClient.cs
index 8d877f6..76bceee 100644
--- a/Source/MQTTnet/Client/MqttClient.cs
+++ b/Source/MQTTnet/Client/MqttClient.cs
@@ -5,6 +5,7 @@ using System.Threading.Tasks;
 using MQTTnet.Adapter;
 using MQTTnet.Client.Connecting;
 using MQTTnet.Client.Disconnecting;
+using MQTTnet.Client.ExtendedAuthenticationExchange;
 using MQTTnet.Client.Options;
 using MQTTnet.Client.Publishing;
 using MQTTnet.Client.Receiving;
@@ -138,6 +139,23 @@ namespace MQTTnet.Client
             }
         }
 
+        public Task SendExtendedAuthenticationExchangeDataAsync(MqttExtendedAuthenticationExchangeData data, CancellationToken cancellationToken)
+        {
+            if (data == null) throw new ArgumentNullException(nameof(data));
+
+            return SendAsync(new MqttAuthPacket
+            {
+                Properties = new MqttAuthPacketProperties
+                {
+                    // This must always be equal to the value from the CONNECT packet. So we use it here to ensure that.
+                    AuthenticationMethod = Options.AuthenticationMethod, 
+                    AuthenticationData = data.AuthenticationData,
+                    ReasonString = data.ReasonString,
+                    UserProperties = data.UserProperties
+                }
+            }, cancellationToken);
+        }
+
         public async Task<MqttClientSubscribeResult> SubscribeAsync(MqttClientSubscribeOptions options, CancellationToken cancellationToken)
         {
             if (options == null) throw new ArgumentNullException(nameof(options));
@@ -474,6 +492,14 @@ namespace MQTTnet.Client
 
                     await DisconnectAsync(null, cancellationToken).ConfigureAwait(false);
                 }
+                else if (packet is MqttAuthPacket authPacket)
+                {
+                    var extendedAuthenticationExchangeHandler = Options.ExtendedAuthenticationExchangeHandler;
+                    if (extendedAuthenticationExchangeHandler != null)
+                    {
+                        await extendedAuthenticationExchangeHandler.HandleRequestAsync(new MqttExtendedAuthenticationExchangeContext(authPacket, this)).ConfigureAwait(false);
+                    }
+                }
                 else
                 {
                     _packetDispatcher.Dispatch(packet);
diff --git a/Source/MQTTnet/Client/MqttClientExtensions.cs b/Source/MQTTnet/Client/MqttClientExtensions.cs
index e5e3cd7..58040f7 100644
--- a/Source/MQTTnet/Client/MqttClientExtensions.cs
+++ b/Source/MQTTnet/Client/MqttClientExtensions.cs
@@ -4,6 +4,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using MQTTnet.Client.Connecting;
 using MQTTnet.Client.Disconnecting;
+using MQTTnet.Client.ExtendedAuthenticationExchange;
 using MQTTnet.Client.Options;
 using MQTTnet.Client.Publishing;
 using MQTTnet.Client.Receiving;
@@ -170,21 +171,36 @@ namespace MQTTnet.Client
 
         public static Task<MqttClientAuthenticateResult> ConnectAsync(this IMqttClient client, IMqttClientOptions options)
         {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+
             return client.ConnectAsync(options, CancellationToken.None);
         }
 
         public static Task DisconnectAsync(this IMqttClient client, MqttClientDisconnectOptions options)
         {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+
             return client.DisconnectAsync(options, CancellationToken.None);
         }
 
+        public static Task SendExtendedAuthenticationExchangeDataAsync(this IMqttClient client, MqttExtendedAuthenticationExchangeData data)
+        {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+
+            return client.SendExtendedAuthenticationExchangeDataAsync(data, CancellationToken.None);
+        }
+
         public static Task<MqttClientSubscribeResult> SubscribeAsync(this IMqttClient client, MqttClientSubscribeOptions options)
         {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+
             return client.SubscribeAsync(options, CancellationToken.None);
         }
 
         public static Task<MqttClientUnsubscribeResult> UnsubscribeAsync(this IMqttClient client, MqttClientUnsubscribeOptions options)
         {
+            if (client == null) throw new ArgumentNullException(nameof(client));
+
             return client.UnsubscribeAsync(options, CancellationToken.None);
         }
 
diff --git a/Source/MQTTnet/Client/Options/IMqttClientOptions.cs b/Source/MQTTnet/Client/Options/IMqttClientOptions.cs
index 3150baa..822603d 100644
--- a/Source/MQTTnet/Client/Options/IMqttClientOptions.cs
+++ b/Source/MQTTnet/Client/Options/IMqttClientOptions.cs
@@ -1,4 +1,5 @@
 using System;
+using MQTTnet.Client.ExtendedAuthenticationExchange;
 using MQTTnet.Formatter;
 
 namespace MQTTnet.Client.Options
@@ -8,6 +9,7 @@ namespace MQTTnet.Client.Options
         string ClientId { get; }
         bool CleanSession { get; }
         IMqttClientCredentials Credentials { get; }
+        IMqttExtendedAuthenticationExchangeHandler ExtendedAuthenticationExchangeHandler { get; }
         MqttProtocolVersion ProtocolVersion { get; }
         IMqttClientChannelOptions ChannelOptions { get; }
         
diff --git a/Source/MQTTnet/Client/Options/MqttClientOptions.cs b/Source/MQTTnet/Client/Options/MqttClientOptions.cs
index be9dc7b..c47f5c6 100644
--- a/Source/MQTTnet/Client/Options/MqttClientOptions.cs
+++ b/Source/MQTTnet/Client/Options/MqttClientOptions.cs
@@ -1,4 +1,5 @@
 using System;
+using MQTTnet.Client.ExtendedAuthenticationExchange;
 using MQTTnet.Formatter;
 
 namespace MQTTnet.Client.Options
@@ -8,6 +9,7 @@ namespace MQTTnet.Client.Options
         public string ClientId { get; set; } = Guid.NewGuid().ToString("N");
         public bool CleanSession { get; set; } = true;
         public IMqttClientCredentials Credentials { get; set; }
+        public IMqttExtendedAuthenticationExchangeHandler ExtendedAuthenticationExchangeHandler { get; set; }
         public MqttProtocolVersion ProtocolVersion { get; set; } = MqttProtocolVersion.V311;
 
         public IMqttClientChannelOptions ChannelOptions { get; set; }
diff --git a/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs b/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs
index c4d7e6c..25563fe 100644
--- a/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs
+++ b/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Linq;
+using MQTTnet.Client.ExtendedAuthenticationExchange;
 using MQTTnet.Formatter;
 
 namespace MQTTnet.Client.Options
@@ -125,6 +126,12 @@ namespace MQTTnet.Client.Options
             return this;
         }
 
+        public MqttClientOptionsBuilder WithExtendedAuthenticationExchangeHandler(IMqttExtendedAuthenticationExchangeHandler handler)
+        {
+            _options.ExtendedAuthenticationExchangeHandler = handler;
+            return this;
+        }
+
         public MqttClientOptionsBuilder WithTcpServer(string server, int? port = null)
         {
             _tcpOptions = new MqttClientTcpOptions
diff --git a/Source/MQTTnet/Formatter/V3/MqttV310PacketFormatter.cs b/Source/MQTTnet/Formatter/V3/MqttV310PacketFormatter.cs
index 70af10e..56ffab6 100644
--- a/Source/MQTTnet/Formatter/V3/MqttV310PacketFormatter.cs
+++ b/Source/MQTTnet/Formatter/V3/MqttV310PacketFormatter.cs
@@ -10,7 +10,11 @@ namespace MQTTnet.Formatter.V3
     public class MqttV310PacketFormatter : IMqttPacketFormatter
     {
         private const int FixedHeaderSize = 1;
-        
+
+        private static readonly MqttPingReqPacket PingReqPacket = new MqttPingReqPacket();
+        private static readonly MqttPingRespPacket PingRespPacket = new MqttPingRespPacket();
+        private static readonly MqttDisconnectPacket DisconnectPacket = new MqttDisconnectPacket();
+
         private readonly IMqttPacketWriter _packetWriter;
 
         public MqttV310PacketFormatter()
@@ -67,14 +71,14 @@ namespace MQTTnet.Formatter.V3
             {
                 case MqttControlPacketType.Connect: return DecodeConnectPacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.ConnAck: return DecodeConnAckPacket(receivedMqttPacket.Body);
-                case MqttControlPacketType.Disconnect: return new MqttDisconnectPacket();
+                case MqttControlPacketType.Disconnect: return DisconnectPacket;
                 case MqttControlPacketType.Publish: return DecodePublishPacket(receivedMqttPacket);
                 case MqttControlPacketType.PubAck: return DecodePubAckPacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.PubRec: return DecodePubRecPacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.PubRel: return DecodePubRelPacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.PubComp: return DecodePubCompPacket(receivedMqttPacket.Body);
-                case MqttControlPacketType.PingReq: return new MqttPingReqPacket();
-                case MqttControlPacketType.PingResp: return new MqttPingRespPacket();
+                case MqttControlPacketType.PingReq: return PingReqPacket;
+                case MqttControlPacketType.PingResp: return PingRespPacket;
                 case MqttControlPacketType.Subscribe: return DecodeSubscribePacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.SubAck: return DecodeSubAckPacket(receivedMqttPacket.Body);
                 case MqttControlPacketType.Unsubscibe: return DecodeUnsubscribePacket(receivedMqttPacket.Body);
@@ -229,7 +233,7 @@ namespace MQTTnet.Formatter.V3
 
             if (!receivedMqttPacket.Body.EndOfStream)
             {
-                packet.Payload = receivedMqttPacket.Body.ReadRemainingData().ToArray();
+                packet.Payload = receivedMqttPacket.Body.ReadRemainingData();
             }
 
             return packet;
diff --git a/Source/MQTTnet/Formatter/V5/MqttV500DataConverter.cs b/Source/MQTTnet/Formatter/V5/MqttV500DataConverter.cs
index 9276617..203181b 100644
--- a/Source/MQTTnet/Formatter/V5/MqttV500DataConverter.cs
+++ b/Source/MQTTnet/Formatter/V5/MqttV500DataConverter.cs
@@ -160,7 +160,7 @@ namespace MQTTnet.Formatter.V5
 
             packet.TopicFilters.AddRange(options.TopicFilters);
             packet.Properties.SubscriptionIdentifier = options.SubscriptionIdentifier;
-            packet.Properties.UserProperties.AddRange(options.UserProperties);
+            packet.Properties.UserProperties = options.UserProperties;
 
             return packet;
         }
@@ -175,7 +175,7 @@ namespace MQTTnet.Formatter.V5
             };
 
             packet.TopicFilters.AddRange(options.TopicFilters);
-            packet.Properties.UserProperties.AddRange(options.UserProperties);
+            packet.Properties.UserProperties = options.UserProperties;
 
             return packet;
         }
diff --git a/Source/MQTTnet/Formatter/V5/MqttV500PacketDecoder.cs b/Source/MQTTnet/Formatter/V5/MqttV500PacketDecoder.cs
index 4c394e4..701c338 100644
--- a/Source/MQTTnet/Formatter/V5/MqttV500PacketDecoder.cs
+++ b/Source/MQTTnet/Formatter/V5/MqttV500PacketDecoder.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using MQTTnet.Adapter;
 using MQTTnet.Exceptions;
 using MQTTnet.Packets;
@@ -10,6 +9,10 @@ namespace MQTTnet.Formatter.V5
 {
     public class MqttV500PacketDecoder
     {
+        private static readonly MqttPingReqPacket PingReqPacket = new MqttPingReqPacket();
+
+        private static readonly MqttPingRespPacket PingRespPacket = new MqttPingRespPacket();
+
         public MqttBasePacket Decode(ReceivedMqttPacket receivedMqttPacket)
         {
             if (receivedMqttPacket == null) throw new ArgumentNullException(nameof(receivedMqttPacket));
@@ -46,10 +49,7 @@ namespace MQTTnet.Formatter.V5
         {
             ThrowIfBodyIsEmpty(body);
 
-            var packet = new MqttConnectPacket
-            {
-                Properties = new MqttConnectPacketProperties()
-            };
+            var packet = new MqttConnectPacket();
 
             var protocolName = body.ReadStringWithLengthPrefix();
             var protocolVersion = body.ReadByte();
@@ -84,6 +84,11 @@ namespace MQTTnet.Formatter.V5
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttConnectPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.SessionExpiryInterval)
                 {
                     packet.Properties.SessionExpiryInterval = propertiesReader.ReadSessionExpiryInterval();
@@ -118,6 +123,11 @@ namespace MQTTnet.Formatter.V5
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -213,13 +223,17 @@ namespace MQTTnet.Formatter.V5
             var packet = new MqttConnAckPacket
             {
                 IsSessionPresent = (acknowledgeFlags & 0x1) > 0,
-                ReasonCode = (MqttConnectReasonCode)body.ReadByte(),
-                Properties = new MqttConnAckPacketProperties()
+                ReasonCode = (MqttConnectReasonCode)body.ReadByte()
             };
 
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttConnAckPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.SessionExpiryInterval)
                 {
                     packet.Properties.SessionExpiryInterval = propertiesReader.ReadSessionExpiryInterval();
@@ -282,6 +296,11 @@ namespace MQTTnet.Formatter.V5
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -299,13 +318,17 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttDisconnectPacket
             {
-                ReasonCode = (MqttDisconnectReasonCode)body.ReadByte(),
-                Properties = new MqttDisconnectPacketProperties()
+                ReasonCode = (MqttDisconnectReasonCode)body.ReadByte()
             };
 
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttDisconnectPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.SessionExpiryInterval)
                 {
                     packet.Properties.SessionExpiryInterval = propertiesReader.ReadSessionExpiryInterval();
@@ -320,6 +343,11 @@ namespace MQTTnet.Formatter.V5
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -337,19 +365,28 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttSubscribePacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttSubscribePacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttSubscribePacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.SubscriptionIdentifier)
                 {
                     packet.Properties.SubscriptionIdentifier = propertiesReader.ReadSubscriptionIdentifier();
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -387,19 +424,28 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttSubAckPacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttSubAckPacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttSubAckPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.ReasonString)
                 {
                     packet.Properties.ReasonString = propertiesReader.ReadReasonString();
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -423,15 +469,24 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttUnsubscribePacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttUnsubscribePacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttUnsubscribePacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -454,19 +509,28 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttUnsubAckPacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttUnsubAckPacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttUnsubAckPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.ReasonString)
                 {
                     packet.Properties.ReasonString = propertiesReader.ReadReasonString();
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -486,12 +550,12 @@ namespace MQTTnet.Formatter.V5
 
         private static MqttBasePacket DecodePingReqPacket()
         {
-            return new MqttPingReqPacket();
+            return PingReqPacket;
         }
 
         private static MqttBasePacket DecodePingRespPacket()
         {
-            return new MqttPingRespPacket();
+            return PingRespPacket;
         }
 
         private static MqttBasePacket DecodePublishPacket(byte header, IMqttPacketBodyReader body)
@@ -507,8 +571,7 @@ namespace MQTTnet.Formatter.V5
                 Topic = body.ReadStringWithLengthPrefix(),
                 Retain = retain,
                 QualityOfServiceLevel = qos,
-                Dup = dup,
-                Properties = new MqttPublishPacketProperties()
+                Dup = dup
             };
 
             if (qos > 0)
@@ -519,6 +582,11 @@ namespace MQTTnet.Formatter.V5
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttPublishPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.PayloadFormatIndicator)
                 {
                     packet.Properties.PayloadFormatIndicator = propertiesReader.ReadPayloadFormatIndicator();
@@ -569,7 +637,7 @@ namespace MQTTnet.Formatter.V5
 
             if (!body.EndOfStream)
             {
-                packet.Payload = body.ReadRemainingData().ToArray();
+                packet.Payload = body.ReadRemainingData();
             }
 
             return packet;
@@ -581,8 +649,7 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttPubAckPacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttPubAckPacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             if (body.EndOfStream)
@@ -596,12 +663,22 @@ namespace MQTTnet.Formatter.V5
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttPubAckPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.ReasonString)
                 {
                     packet.Properties.ReasonString = propertiesReader.ReadReasonString();
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -619,8 +696,7 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttPubRecPacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttPubRecPacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             if (body.EndOfStream)
@@ -634,12 +710,22 @@ namespace MQTTnet.Formatter.V5
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttPubRecPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.ReasonString)
                 {
                     packet.Properties.ReasonString = propertiesReader.ReadReasonString();
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -657,8 +743,7 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttPubRelPacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttPubRelPacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             if (body.EndOfStream)
@@ -672,12 +757,22 @@ namespace MQTTnet.Formatter.V5
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttPubRelPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.ReasonString)
                 {
                     packet.Properties.ReasonString = propertiesReader.ReadReasonString();
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -695,8 +790,7 @@ namespace MQTTnet.Formatter.V5
 
             var packet = new MqttPubCompPacket
             {
-                PacketIdentifier = body.ReadTwoByteInteger(),
-                Properties = new MqttPubCompPacketProperties()
+                PacketIdentifier = body.ReadTwoByteInteger()
             };
 
             if (body.EndOfStream)
@@ -710,12 +804,22 @@ namespace MQTTnet.Formatter.V5
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttPubCompPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.ReasonString)
                 {
                     packet.Properties.ReasonString = propertiesReader.ReadReasonString();
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
@@ -731,10 +835,7 @@ namespace MQTTnet.Formatter.V5
         {
             ThrowIfBodyIsEmpty(body);
 
-            var packet = new MqttAuthPacket
-            {
-                Properties = new MqttAuthPacketProperties()
-            };
+            var packet = new MqttAuthPacket();
 
             if (body.EndOfStream)
             {
@@ -747,6 +848,11 @@ namespace MQTTnet.Formatter.V5
             var propertiesReader = new MqttV500PropertiesReader(body);
             while (propertiesReader.MoveNext())
             {
+                if (packet.Properties == null)
+                {
+                    packet.Properties = new MqttAuthPacketProperties();
+                }
+
                 if (propertiesReader.CurrentPropertyId == MqttPropertyId.AuthenticationMethod)
                 {
                     packet.Properties.AuthenticationMethod = propertiesReader.ReadAuthenticationMethod();
@@ -761,6 +867,11 @@ namespace MQTTnet.Formatter.V5
                 }
                 else if (propertiesReader.CurrentPropertyId == MqttPropertyId.UserProperty)
                 {
+                    if (packet.Properties.UserProperties == null)
+                    {
+                        packet.Properties.UserProperties = new List<MqttUserProperty>();
+                    }
+
                     propertiesReader.AddUserPropertyTo(packet.Properties.UserProperties);
                 }
                 else
diff --git a/Source/MQTTnet/Packets/MqttAuthPacketProperties.cs b/Source/MQTTnet/Packets/MqttAuthPacketProperties.cs
index 6ed25ee..057004d 100644
--- a/Source/MQTTnet/Packets/MqttAuthPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttAuthPacketProperties.cs
@@ -10,6 +10,6 @@ namespace MQTTnet.Packets
 
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttConnAckPacketProperties.cs b/Source/MQTTnet/Packets/MqttConnAckPacketProperties.cs
index 262222d..d59735c 100644
--- a/Source/MQTTnet/Packets/MqttConnAckPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttConnAckPacketProperties.cs
@@ -18,7 +18,7 @@ namespace MQTTnet.Packets
 
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
 
         public bool? WildcardSubscriptionAvailable { get; set; }
 
diff --git a/Source/MQTTnet/Packets/MqttConnectPacketProperties.cs b/Source/MQTTnet/Packets/MqttConnectPacketProperties.cs
index 25cf5bd..4cc405e 100644
--- a/Source/MQTTnet/Packets/MqttConnectPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttConnectPacketProperties.cs
@@ -22,6 +22,6 @@ namespace MQTTnet.Packets
 
         public uint? MaximumPacketSize { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
\ No newline at end of file
diff --git a/Source/MQTTnet/Packets/MqttDisconnectPacketProperties.cs b/Source/MQTTnet/Packets/MqttDisconnectPacketProperties.cs
index a5385cb..e05529f 100644
--- a/Source/MQTTnet/Packets/MqttDisconnectPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttDisconnectPacketProperties.cs
@@ -8,7 +8,7 @@ namespace MQTTnet.Packets
 
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
 
         public string ServerReference { get; set; }
     }
diff --git a/Source/MQTTnet/Packets/MqttPubAckPacketProperties.cs b/Source/MQTTnet/Packets/MqttPubAckPacketProperties.cs
index 061f72f..e2debd4 100644
--- a/Source/MQTTnet/Packets/MqttPubAckPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttPubAckPacketProperties.cs
@@ -6,6 +6,6 @@ namespace MQTTnet.Packets
     {
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttPubCompPacketProperties.cs b/Source/MQTTnet/Packets/MqttPubCompPacketProperties.cs
index c29ad6a..35e040f 100644
--- a/Source/MQTTnet/Packets/MqttPubCompPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttPubCompPacketProperties.cs
@@ -6,6 +6,6 @@ namespace MQTTnet.Packets
     {
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttPubRecPacketProperties.cs b/Source/MQTTnet/Packets/MqttPubRecPacketProperties.cs
index 574bc61..0cd7225 100644
--- a/Source/MQTTnet/Packets/MqttPubRecPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttPubRecPacketProperties.cs
@@ -6,6 +6,6 @@ namespace MQTTnet.Packets
     {
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttPubRelPacketProperties.cs b/Source/MQTTnet/Packets/MqttPubRelPacketProperties.cs
index d7a21f6..aa9625d 100644
--- a/Source/MQTTnet/Packets/MqttPubRelPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttPubRelPacketProperties.cs
@@ -6,6 +6,6 @@ namespace MQTTnet.Packets
     {
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttSubAckPacket.cs b/Source/MQTTnet/Packets/MqttSubAckPacket.cs
index 053e713..4600a4e 100644
--- a/Source/MQTTnet/Packets/MqttSubAckPacket.cs
+++ b/Source/MQTTnet/Packets/MqttSubAckPacket.cs
@@ -8,7 +8,7 @@ namespace MQTTnet.Packets
     {
         public ushort? PacketIdentifier { get; set; }
 
-        public List<MqttSubscribeReturnCode> ReturnCodes { get; } = new List<MqttSubscribeReturnCode>();
+        public List<MqttSubscribeReturnCode> ReturnCodes { get; set; } = new List<MqttSubscribeReturnCode>();
 
         #region Added in MQTTv5.0.0
 
diff --git a/Source/MQTTnet/Packets/MqttSubAckPacketProperties.cs b/Source/MQTTnet/Packets/MqttSubAckPacketProperties.cs
index b2b3eff..74d3e7f 100644
--- a/Source/MQTTnet/Packets/MqttSubAckPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttSubAckPacketProperties.cs
@@ -6,6 +6,6 @@ namespace MQTTnet.Packets
     {
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttSubscribePacket.cs b/Source/MQTTnet/Packets/MqttSubscribePacket.cs
index c96c75b..1ea1685 100644
--- a/Source/MQTTnet/Packets/MqttSubscribePacket.cs
+++ b/Source/MQTTnet/Packets/MqttSubscribePacket.cs
@@ -7,7 +7,7 @@ namespace MQTTnet.Packets
     {
         public ushort? PacketIdentifier { get; set; }
 
-        public List<TopicFilter> TopicFilters { get; } = new List<TopicFilter>();
+        public List<TopicFilter> TopicFilters { get; set; } = new List<TopicFilter>();
 
         #region Added in MQTTv5
 
diff --git a/Source/MQTTnet/Packets/MqttSubscribePacketProperties.cs b/Source/MQTTnet/Packets/MqttSubscribePacketProperties.cs
index 5b92c5f..34f58f2 100644
--- a/Source/MQTTnet/Packets/MqttSubscribePacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttSubscribePacketProperties.cs
@@ -6,6 +6,6 @@ namespace MQTTnet.Packets
     {
         public uint? SubscriptionIdentifier { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttUnsubAckPacket.cs b/Source/MQTTnet/Packets/MqttUnsubAckPacket.cs
index 0b45df6..a17261e 100644
--- a/Source/MQTTnet/Packets/MqttUnsubAckPacket.cs
+++ b/Source/MQTTnet/Packets/MqttUnsubAckPacket.cs
@@ -12,7 +12,7 @@ namespace MQTTnet.Packets
 
         public MqttUnsubAckPacketProperties Properties { get; set; }
 
-        public List<MqttUnsubscribeReasonCode> ReasonCodes { get; } = new List<MqttUnsubscribeReasonCode>();
+        public List<MqttUnsubscribeReasonCode> ReasonCodes { get; set; } = new List<MqttUnsubscribeReasonCode>();
 
         #endregion
 
diff --git a/Source/MQTTnet/Packets/MqttUnsubAckPacketProperties.cs b/Source/MQTTnet/Packets/MqttUnsubAckPacketProperties.cs
index ca444d9..2a102c6 100644
--- a/Source/MQTTnet/Packets/MqttUnsubAckPacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttUnsubAckPacketProperties.cs
@@ -6,6 +6,6 @@ namespace MQTTnet.Packets
     {
         public string ReasonString { get; set; }
 
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }
diff --git a/Source/MQTTnet/Packets/MqttUnsubscribePacket.cs b/Source/MQTTnet/Packets/MqttUnsubscribePacket.cs
index bb1d4c2..7b07a24 100644
--- a/Source/MQTTnet/Packets/MqttUnsubscribePacket.cs
+++ b/Source/MQTTnet/Packets/MqttUnsubscribePacket.cs
@@ -6,7 +6,7 @@ namespace MQTTnet.Packets
     {
         public ushort? PacketIdentifier { get; set; }
 
-        public List<string> TopicFilters { get; } = new List<string>();
+        public List<string> TopicFilters { get; set; } = new List<string>();
 
         #region Added in MQTTv5
 
diff --git a/Source/MQTTnet/Packets/MqttUnsubscribePacketProperties.cs b/Source/MQTTnet/Packets/MqttUnsubscribePacketProperties.cs
index 5fb4d66..3ec68f1 100644
--- a/Source/MQTTnet/Packets/MqttUnsubscribePacketProperties.cs
+++ b/Source/MQTTnet/Packets/MqttUnsubscribePacketProperties.cs
@@ -4,6 +4,6 @@ namespace MQTTnet.Packets
 {
     public class MqttUnsubscribePacketProperties
     {
-        public List<MqttUserProperty> UserProperties { get; } = new List<MqttUserProperty>();
+        public List<MqttUserProperty> UserProperties { get; set; }
     }
 }