From 85a1c681b1b3e3b42a1ec2a2d34003b868e9d850 Mon Sep 17 00:00:00 2001
From: Marco Rossignoli <marco.rossignoli@gmail.com>
Date: Wed, 12 Feb 2020 17:25:10 +0100
Subject: [PATCH] Fix AppDomain.SetPrincipalPolicy bug for new threads (#32104)

* fix principal policy for new threads

Fixes #31717
---
 .../shared/System/Threading/Thread.cs                      | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/System.Private.CoreLib/shared/System/Threading/Thread.cs b/src/System.Private.CoreLib/shared/System/Threading/Thread.cs
index 28b2e6eb8f5a..a2be70c847fc 100644
--- a/src/System.Private.CoreLib/shared/System/Threading/Thread.cs
+++ b/src/System.Private.CoreLib/shared/System/Threading/Thread.cs
@@ -136,11 +136,12 @@ public static IPrincipal? CurrentPrincipal
         {
             get
             {
-                if (s_asyncLocalPrincipal is null)
+                IPrincipal? principal = s_asyncLocalPrincipal?.Value;
+                if (principal is null)
                 {
-                    CurrentPrincipal = AppDomain.CurrentDomain.GetThreadPrincipal();
+                    CurrentPrincipal = (principal = AppDomain.CurrentDomain.GetThreadPrincipal());
                 }
-                return s_asyncLocalPrincipal?.Value;
+                return principal;
             }
             set
             {