diff --git a/src/Microsoft.TestPlatform.TestHostProvider/Hosting/DotnetTestHostManager.cs b/src/Microsoft.TestPlatform.TestHostProvider/Hosting/DotnetTestHostManager.cs
index c0a756e51b..fd2d992697 100644
--- a/src/Microsoft.TestPlatform.TestHostProvider/Hosting/DotnetTestHostManager.cs
+++ b/src/Microsoft.TestPlatform.TestHostProvider/Hosting/DotnetTestHostManager.cs
@@ -553,6 +553,7 @@ bool SilentlyForceToX64()
 
     internal /* for testing purposes */ void ForwardDotnetRootEnvironmentVariable(TestProcessStartInfo startInfo)
     {
+        TPDebug.Assert(_targetFramework is not null, "Initialize must have been called before this method.");
         const string prefix = "VSTEST_WINAPPHOST_";
         const string dotnetRoot = "DOTNET_ROOT";
         string vstestDotnetRootEnvName = $"{prefix}{dotnetRoot}(x86)";