diff --git a/Serilog.Sinks.Network.Test/JsonFormatter.cs b/Serilog.Sinks.Network.Test/JsonFormatter.cs
index 1024d2c..38a6c96 100644
--- a/Serilog.Sinks.Network.Test/JsonFormatter.cs
+++ b/Serilog.Sinks.Network.Test/JsonFormatter.cs
@@ -11,7 +11,7 @@ namespace Serilog.Sinks.Network.Test
 {
     public class JsonFormatter
     {
-        private static LoggerAndSocket ConfigureTestLogger(ITextFormatter formatter = null)
+        private static LoggerAndSocket ConfigureTestLogger(ITextFormatter? formatter = null)
         {
             var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
             socket.Bind(new IPEndPoint(IPAddress.Loopback, 0));
diff --git a/Serilog.Sinks.Network.Test/Serilog.Sinks.Network.Test.csproj b/Serilog.Sinks.Network.Test/Serilog.Sinks.Network.Test.csproj
index 4079197..f7297eb 100644
--- a/Serilog.Sinks.Network.Test/Serilog.Sinks.Network.Test.csproj
+++ b/Serilog.Sinks.Network.Test/Serilog.Sinks.Network.Test.csproj
@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
     <LangVersion>Preview</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Serilog.Formatting.Compact" Version="3.0.0" />
diff --git a/Serilog.Sinks.Network.Test/WhenLoggingViaTcp.cs b/Serilog.Sinks.Network.Test/WhenLoggingViaTcp.cs
index 192e9fb..e82c207 100644
--- a/Serilog.Sinks.Network.Test/WhenLoggingViaTcp.cs
+++ b/Serilog.Sinks.Network.Test/WhenLoggingViaTcp.cs
@@ -15,7 +15,7 @@ namespace Serilog.Sinks.Network.Test
 {
     public class WhenLoggingViaTcp
     {
-        private static LoggerAndSocket ConfigureTestLogger(ITextFormatter formatter = null)
+        private static LoggerAndSocket ConfigureTestLogger(ITextFormatter? formatter = null)
         {
             var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
             socket.Bind(new IPEndPoint(IPAddress.Loopback, 0));
@@ -66,7 +66,7 @@ public async Task CanLogWithProperties()
             using var fixture = ConfigureTestLogger();
             fixture.Logger.Information("TCP Hello {location}", "world");
             var receivedData = await ServerPoller.PollForReceivedData(fixture.Socket);
-            dynamic payload = JsonConvert.DeserializeObject<ExpandoObject>(receivedData);
+            dynamic? payload = JsonConvert.DeserializeObject<ExpandoObject>(receivedData);
             if (payload == null)
             {
                 throw new AssertionFailedException("expected payload not null");
diff --git a/Serilog.Sinks.Network.Test/WhenLoggingViaUdp.cs b/Serilog.Sinks.Network.Test/WhenLoggingViaUdp.cs
index e220d81..b1b0c36 100644
--- a/Serilog.Sinks.Network.Test/WhenLoggingViaUdp.cs
+++ b/Serilog.Sinks.Network.Test/WhenLoggingViaUdp.cs
@@ -15,7 +15,7 @@ namespace Serilog.Sinks.Network.Test
 {
     public class WhenLoggingViaUdp 
     {
-        private static LoggerAndSocket ConfigureTestLogger(ITextFormatter formatter = null)
+        private static LoggerAndSocket ConfigureTestLogger(ITextFormatter? formatter = null)
         {
             var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
             socket.Bind(new IPEndPoint(IPAddress.Loopback, 0));