diff --git a/src/BenchmarkDotNet.Diagnostics.dotTrace/BenchmarkDotNet.Diagnostics.dotTrace.csproj b/src/BenchmarkDotNet.Diagnostics.dotTrace/BenchmarkDotNet.Diagnostics.dotTrace.csproj
index e4037e5bcf..e7852f1575 100644
--- a/src/BenchmarkDotNet.Diagnostics.dotTrace/BenchmarkDotNet.Diagnostics.dotTrace.csproj
+++ b/src/BenchmarkDotNet.Diagnostics.dotTrace/BenchmarkDotNet.Diagnostics.dotTrace.csproj
@@ -6,6 +6,7 @@
         <AssemblyTitle>BenchmarkDotNet.Diagnostics.dotTrace</AssemblyTitle>
         <AssemblyName>BenchmarkDotNet.Diagnostics.dotTrace</AssemblyName>
         <PackageId>BenchmarkDotNet.Diagnostics.dotTrace</PackageId>
+        <Nullable>enable</Nullable>
     </PropertyGroup>
 
     <ItemGroup>
diff --git a/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoser.cs b/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoser.cs
index a53c305938..1b3186124b 100644
--- a/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoser.cs
+++ b/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoser.cs
@@ -19,10 +19,10 @@ namespace BenchmarkDotNet.Diagnostics.dotTrace
 {
     public class DotTraceDiagnoser : IProfiler
     {
-        private readonly Uri nugetUrl;
-        private readonly string toolsDownloadFolder;
+        private readonly Uri? nugetUrl;
+        private readonly string? toolsDownloadFolder;
 
-        public DotTraceDiagnoser(Uri nugetUrl = null, string toolsDownloadFolder = null)
+        public DotTraceDiagnoser(Uri? nugetUrl = null, string? toolsDownloadFolder = null)
         {
             this.nugetUrl = nugetUrl;
             this.toolsDownloadFolder = toolsDownloadFolder;
diff --git a/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoserAttribute.cs b/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoserAttribute.cs
index de803e6443..19e88a6de1 100644
--- a/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoserAttribute.cs
+++ b/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceDiagnoserAttribute.cs
@@ -13,7 +13,7 @@ public DotTraceDiagnoserAttribute()
             Config = ManualConfig.CreateEmpty().AddDiagnoser(new DotTraceDiagnoser());
         }
 
-        public DotTraceDiagnoserAttribute(Uri nugetUrl = null, string toolsDownloadFolder = null)
+        public DotTraceDiagnoserAttribute(Uri? nugetUrl = null, string? toolsDownloadFolder = null)
         {
             Config = ManualConfig.CreateEmpty().AddDiagnoser(new DotTraceDiagnoser(nugetUrl, toolsDownloadFolder));
         }
diff --git a/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceToolBase.cs b/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceToolBase.cs
index c41ffc53e5..f2f07625fa 100644
--- a/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceToolBase.cs
+++ b/src/BenchmarkDotNet.Diagnostics.dotTrace/DotTraceToolBase.cs
@@ -11,11 +11,11 @@ namespace BenchmarkDotNet.Diagnostics.dotTrace
     internal abstract class DotTraceToolBase
     {
         private readonly ILogger logger;
-        private readonly Uri nugetUrl;
+        private readonly Uri? nugetUrl;
         private readonly NuGetApi nugetApi;
-        private readonly string downloadTo;
+        private readonly string? downloadTo;
 
-        protected DotTraceToolBase(ILogger logger, Uri nugetUrl = null, NuGetApi nugetApi = NuGetApi.V3, string downloadTo = null)
+        protected DotTraceToolBase(ILogger logger, Uri? nugetUrl = null, NuGetApi nugetApi = NuGetApi.V3, string? downloadTo = null)
         {
             this.logger = logger;
             this.nugetUrl = nugetUrl;
@@ -48,9 +48,9 @@ public void Init(DiagnoserActionParameters parameters)
         public string Start(DiagnoserActionParameters parameters)
         {
             string snapshotFile = ArtifactFileNameHelper.GetFilePath(parameters, "snapshots", DateTime.Now, "dtp", ".0000".Length);
-            string snapshotDirectory = Path.GetDirectoryName(snapshotFile);
+            string? snapshotDirectory = Path.GetDirectoryName(snapshotFile);
             logger.WriteLineInfo($"Target snapshot file: {snapshotFile}");
-            if (!Directory.Exists(snapshotDirectory))
+            if (!Directory.Exists(snapshotDirectory) && snapshotDirectory != null)
             {
                 try
                 {
@@ -126,7 +126,7 @@ protected string GetRunnerPath()
             if (consoleRunnerPackageField == null)
                 throw new InvalidOperationException("Field 'ConsoleRunnerPackage' not found.");
 
-            object consoleRunnerPackage = consoleRunnerPackageField.GetValue(null);
+            object? consoleRunnerPackage = consoleRunnerPackageField.GetValue(null);
             if (consoleRunnerPackage == null)
                 throw new InvalidOperationException("Unable to get value of 'ConsoleRunnerPackage'.");
 
@@ -135,7 +135,7 @@ protected string GetRunnerPath()
             if (getRunnerPathMethod == null)
                 throw new InvalidOperationException("Method 'GetRunnerPath' not found.");
 
-            string runnerPath = getRunnerPathMethod.Invoke(consoleRunnerPackage, null) as string;
+            string? runnerPath = getRunnerPathMethod.Invoke(consoleRunnerPackage, null) as string;
             if (runnerPath == null)
                 throw new InvalidOperationException("Unable to invoke 'GetRunnerPath'.");
 
diff --git a/src/BenchmarkDotNet.Diagnostics.dotTrace/ExternalDotTraceTool.cs b/src/BenchmarkDotNet.Diagnostics.dotTrace/ExternalDotTraceTool.cs
index 9c5161b309..dfc9903b82 100644
--- a/src/BenchmarkDotNet.Diagnostics.dotTrace/ExternalDotTraceTool.cs
+++ b/src/BenchmarkDotNet.Diagnostics.dotTrace/ExternalDotTraceTool.cs
@@ -12,7 +12,7 @@ internal class ExternalDotTraceTool : DotTraceToolBase
     {
         private static readonly TimeSpan AttachTimeout = TimeSpan.FromMinutes(5);
 
-        public ExternalDotTraceTool(ILogger logger, Uri nugetUrl = null, NuGetApi nugetApi = NuGetApi.V3, string downloadTo = null) :
+        public ExternalDotTraceTool(ILogger logger, Uri? nugetUrl = null, NuGetApi nugetApi = NuGetApi.V3, string? downloadTo = null) :
             base(logger, nugetUrl, nugetApi, downloadTo) { }
 
         protected override bool AttachOnly => true;
@@ -44,7 +44,7 @@ protected override void Attach(DiagnoserActionParameters parameters, string snap
             {
                 process.OutputDataReceived += (_, args) =>
                 {
-                    string content = args.Data;
+                    string? content = args.Data;
                     if (content != null)
                     {
                         logger.WriteLineInfo("[dotTrace] " + content);
@@ -54,7 +54,7 @@ protected override void Attach(DiagnoserActionParameters parameters, string snap
                 };
                 process.ErrorDataReceived += (_, args) =>
                 {
-                    string content = args.Data;
+                    string? content = args.Data;
                     if (content != null)
                         logger.WriteLineError("[dotTrace] " + args.Data);
                 };
diff --git a/src/BenchmarkDotNet.Diagnostics.dotTrace/InProcessDotTraceTool.cs b/src/BenchmarkDotNet.Diagnostics.dotTrace/InProcessDotTraceTool.cs
index a124e3e495..a02c9c1995 100644
--- a/src/BenchmarkDotNet.Diagnostics.dotTrace/InProcessDotTraceTool.cs
+++ b/src/BenchmarkDotNet.Diagnostics.dotTrace/InProcessDotTraceTool.cs
@@ -7,7 +7,7 @@ namespace BenchmarkDotNet.Diagnostics.dotTrace
 {
     internal class InProcessDotTraceTool : DotTraceToolBase
     {
-        public InProcessDotTraceTool(ILogger logger, Uri nugetUrl = null, NuGetApi nugetApi = NuGetApi.V3, string downloadTo = null) :
+        public InProcessDotTraceTool(ILogger logger, Uri? nugetUrl = null, NuGetApi nugetApi = NuGetApi.V3, string? downloadTo = null) :
             base(logger, nugetUrl, nugetApi, downloadTo) { }
 
         protected override bool AttachOnly => false;
diff --git a/src/BenchmarkDotNet.Diagnostics.dotTrace/Progress.cs b/src/BenchmarkDotNet.Diagnostics.dotTrace/Progress.cs
index 1d8249f31e..c353939f1f 100644
--- a/src/BenchmarkDotNet.Diagnostics.dotTrace/Progress.cs
+++ b/src/BenchmarkDotNet.Diagnostics.dotTrace/Progress.cs
@@ -18,7 +18,7 @@ public Progress(ILogger logger, string title)
         }
 
         private int lastProgress;
-        private Stopwatch stopwatch;
+        private Stopwatch? stopwatch;
 
         public void Report(double value)
         {