diff --git a/browser/app/profile/001-base-profile.js b/browser/app/profile/001-base-profile.js
index 5169273886a7f1da3098e13b931f333ecc61751d..e3180a5eaba45fbf435e06ede99774a69685e23f 100644
--- a/browser/app/profile/001-base-profile.js
+++ b/browser/app/profile/001-base-profile.js
@@ -268,7 +268,7 @@ pref("network.http.referer.defaultPolicy.pbmode", 2);
 pref("network.http.referer.XOriginTrimmingPolicy", 2); // Bug 17228: Force trim referer to scheme+host+port in cross-origin requests
 pref("media.videocontrols.picture-in-picture.enabled", false); // Bug 40148: disable until audited in #40147
 // Bug 40463: Disable Windows SSO
-pref("network.http.windows-sso.enabled", false);
+pref("network.http.windows-sso.enabled", false, locked);
 // Bug 40383: Disable new PerformanceEventTiming
 pref("dom.enable_event_timing", false);
 // Disable API for measuring text width and height.