diff --git a/src/installer/tests/Microsoft.NET.HostModel.Tests/AppHost.Bundle.Tests/BundledAppWithSubDirs.cs b/src/installer/tests/Microsoft.NET.HostModel.Tests/AppHost.Bundle.Tests/BundledAppWithSubDirs.cs
index 6621259213815..6ac7a6b2a5599 100644
--- a/src/installer/tests/Microsoft.NET.HostModel.Tests/AppHost.Bundle.Tests/BundledAppWithSubDirs.cs
+++ b/src/installer/tests/Microsoft.NET.HostModel.Tests/AppHost.Bundle.Tests/BundledAppWithSubDirs.cs
@@ -2,12 +2,16 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Threading;
+using System.Diagnostics;
 using BundleTests.Helpers;
 using Microsoft.DotNet.Cli.Build.Framework;
 using Microsoft.DotNet.CoreSetup.Test;
 using Microsoft.NET.HostModel.Bundle;
 using Xunit;
 
+[assembly: CollectionBehavior(DisableTestParallelization = true)]
+
 namespace AppHost.Bundle.Tests
 {
     public class BundledAppWithSubDirs : BundleTestBase, IClassFixture<BundledAppWithSubDirs.SharedTestState>
diff --git a/src/installer/tests/Microsoft.NET.HostModel.Tests/Microsoft.NET.HostModel.Bundle.Tests/BundleAndRun.cs b/src/installer/tests/Microsoft.NET.HostModel.Tests/Microsoft.NET.HostModel.Bundle.Tests/BundleAndRun.cs
index e4e5cc57c0897..3c75259da7c31 100644
--- a/src/installer/tests/Microsoft.NET.HostModel.Tests/Microsoft.NET.HostModel.Bundle.Tests/BundleAndRun.cs
+++ b/src/installer/tests/Microsoft.NET.HostModel.Tests/Microsoft.NET.HostModel.Bundle.Tests/BundleAndRun.cs
@@ -9,6 +9,8 @@
 using BundleTests.Helpers;
 using System.Runtime.InteropServices;
 
+[assembly: CollectionBehavior(DisableTestParallelization = true)]
+
 namespace Microsoft.NET.HostModel.Tests
 {
     public class BundleAndRun : IClassFixture<BundleAndRun.SharedTestState>
diff --git a/src/installer/tests/TestUtils/TestProjectFixture.cs b/src/installer/tests/TestUtils/TestProjectFixture.cs
index 7b9da29d1a908..2da1541a8105b 100644
--- a/src/installer/tests/TestUtils/TestProjectFixture.cs
+++ b/src/installer/tests/TestUtils/TestProjectFixture.cs
@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Threading;
 
 namespace Microsoft.DotNet.CoreSetup.Test
 {
@@ -75,10 +76,23 @@ public void Dispose()
             }
         }
 
+        static readonly object s_lock = new object();
+
         private TestProject CopyTestProject(TestProject sourceTestProject)
         {
+            // This can race with the filesystem. If we're running this code from two threads, fail fast
+            bool lockTaken = false;
+            object lockObj = s_lock;
+            Monitor.TryEnter(lockObj, 0, ref lockTaken);
+            if (!lockTaken)
+            {
+                throw new InvalidOperationException("Lock is held, test should not be executed in parallel");
+            }
+
             EnsureDirectoryBuildFiles(TestArtifact.TestArtifactsPath);
             return sourceTestProject.Copy();
+
+            // Don't release the lock. There should be only one thread running these tests
         }
 
         private void EnsureDirectoryBuildFiles(string testArtifactDirectory)