--- a/browser/modules/ContextMenu.jsm
+++ b/browser/modules/ContextMenu.jsm
@@ -654,17 +654,17 @@ class ContextMenu {
       // used for nsContextMenu.initLeaveDOMFullScreenItems and
       // nsContextMenu.initMediaPlayerItems
       fullscreen: context.target.ownerDocument.fullscreen,
 
       // used for nsContextMenu.initMiscItems
       contentType: context.target.ownerDocument.contentType,
 
       // used for nsContextMenu.saveLink
-      isPrivate: PrivateBrowsingUtils.isBrowserPrivate(context.target.ownerDocument),
+      isPrivate: PrivateBrowsingUtils.isContentWindowPrivate(context.target.ownerGlobal),
     };
 
     // used for nsContextMenu.initMediaPlayerItems
     Object.assign(cleanTarget, {
       ended: context.target.ended,
       muted: context.target.muted,
       paused: context.target.paused,
       controls: context.target.controls,