--- a/browser/components/preferences/in-content/main.js
+++ b/browser/components/preferences/in-content/main.js
@@ -926,23 +926,21 @@ var gMainPane = {
     if (count == 0) {
       Services.prefs.setBoolPref("privacy.userContext.enabled", false);
       return;
     }
 
     let [
       title, message, okButton, cancelButton
     ] = await document.l10n.formatValues([
-      "containers-disable-alert-title",
-      "containers-disable-alert-desc",
-      "containers-disable-alert-ok-button",
-      "containers-disable-alert-cancel-button"
-    ], {
-      tabCount: count
-    });
+      ["containers-disable-alert-title"],
+      ["containers-disable-alert-desc", { tabCount: count }],
+      ["containers-disable-alert-ok-button", { tabCount: count }],
+      ["containers-disable-alert-cancel-button"]
+    ]);
 
     let buttonFlags = (Ci.nsIPrompt.BUTTON_TITLE_IS_STRING * Ci.nsIPrompt.BUTTON_POS_0) +
       (Ci.nsIPrompt.BUTTON_TITLE_IS_STRING * Ci.nsIPrompt.BUTTON_POS_1);
 
     let rv = Services.prompt.confirmEx(window, title, message, buttonFlags,
       okButton, cancelButton, null, null, {});
     if (rv == 0) {
       Services.prefs.setBoolPref("privacy.userContext.enabled", false);