diff --git a/src/System.Management.Automation/utils/tracing/EtwActivityReverter.cs b/src/System.Management.Automation/utils/tracing/EtwActivityReverter.cs
index a7a257ceb21..c235f09b888 100644
--- a/src/System.Management.Automation/utils/tracing/EtwActivityReverter.cs
+++ b/src/System.Management.Automation/utils/tracing/EtwActivityReverter.cs
@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+#nullable enable
 #if !UNIX
 
 namespace System.Management.Automation.Tracing