diff --git a/test/OpenTelemetry.Instrumentation.Owin.Tests/Controllers/TestController.cs b/test/OpenTelemetry.Instrumentation.Owin.Tests/Controllers/TestController.cs
index bf7f20b9ae..d6d9145462 100644
--- a/test/OpenTelemetry.Instrumentation.Owin.Tests/Controllers/TestController.cs
+++ b/test/OpenTelemetry.Instrumentation.Owin.Tests/Controllers/TestController.cs
@@ -8,7 +8,7 @@ namespace OpenTelemetry.Instrumentation.Owin.Tests.Controllers;
 public class TestController : ApiController
 {
     // GET api/test/{id}
-    public string Get(string id = null)
+    public string Get(string? id = null)
     {
         return $"id:{id}";
     }
diff --git a/test/OpenTelemetry.Instrumentation.Owin.Tests/DiagnosticsMiddlewareTests.cs b/test/OpenTelemetry.Instrumentation.Owin.Tests/DiagnosticsMiddlewareTests.cs
index fa89a01b00..d2111ab468 100644
--- a/test/OpenTelemetry.Instrumentation.Owin.Tests/DiagnosticsMiddlewareTests.cs
+++ b/test/OpenTelemetry.Instrumentation.Owin.Tests/DiagnosticsMiddlewareTests.cs
@@ -22,19 +22,18 @@ namespace OpenTelemetry.Instrumentation.Owin.Tests;
 public class DiagnosticsMiddlewareTests : IDisposable
 {
     private readonly Uri serviceBaseUri;
-    private readonly IDisposable listener;
+    private readonly IDisposable? listener;
     private readonly EventWaitHandle requestCompleteHandle = new(false, EventResetMode.AutoReset);
 
     public DiagnosticsMiddlewareTests()
     {
         Random random = new Random();
         var retryCount = 5;
-        while (retryCount > 0)
+        do
         {
+            this.serviceBaseUri = new Uri($"http://localhost:{random.Next(2000, 5000)}/");
             try
             {
-                this.serviceBaseUri = new Uri($"http://localhost:{random.Next(2000, 5000)}/");
-
                 this.listener = WebApp.Start(
                     this.serviceBaseUri.ToString(),
                     appBuilder =>
@@ -81,6 +80,7 @@ public DiagnosticsMiddlewareTests()
                 retryCount--;
             }
         }
+        while (retryCount > 0);
 
         if (this.listener == null)
         {
diff --git a/test/OpenTelemetry.Instrumentation.Owin.Tests/OpenTelemetry.Instrumentation.Owin.Tests.csproj b/test/OpenTelemetry.Instrumentation.Owin.Tests/OpenTelemetry.Instrumentation.Owin.Tests.csproj
index 1ef3fee142..e61f3950e7 100644
--- a/test/OpenTelemetry.Instrumentation.Owin.Tests/OpenTelemetry.Instrumentation.Owin.Tests.csproj
+++ b/test/OpenTelemetry.Instrumentation.Owin.Tests/OpenTelemetry.Instrumentation.Owin.Tests.csproj
@@ -3,7 +3,6 @@
   <PropertyGroup>
     <Description>Unit test project for OpenTelemetry OWIN instrumentation</Description>
     <TargetFrameworks>$(NetFrameworkMinimumSupportedVersion)</TargetFrameworks>
-    <Nullable>disable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>