--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -7545,18 +7545,18 @@ var gPrivateBrowsingUI = {
         // Adjust the New Window menu entries
         [
           { normal: "menu_newNavigator", private: "menu_newPrivateWindow" },
         ].forEach(function(menu) {
           let newWindow = document.getElementById(menu.normal);
           let newPrivateWindow = document.getElementById(menu.private);
           if (newWindow && newPrivateWindow) {
             newPrivateWindow.hidden = true;
-            newWindow.label = newPrivateWindow.label;
-            newWindow.accessKey = newPrivateWindow.accessKey;
+            newWindow.setAttribute(
+              'data-l10n-id', newPrivateWindow.getAttribute('data-l10n-id'));
             newWindow.command = newPrivateWindow.command;
           }
         });
       }
     }
 
     let urlBarSearchParam = gURLBar.getAttribute("autocompletesearchparam") || "";
     if (!PrivateBrowsingUtils.permanentPrivateBrowsing &&