diff --git a/toolkit/modules/AppConstants.sys.mjs b/toolkit/modules/AppConstants.sys.mjs
index 5465ed3fb01e4214029b44f338d5e1e1580c3aab..a4d6b42916014d5e0f643b35a7b4feb281f59023 100644
--- a/toolkit/modules/AppConstants.sys.mjs
+++ b/toolkit/modules/AppConstants.sys.mjs
@@ -172,6 +172,8 @@ export var AppConstants = Object.freeze({
   MOZ_UPDATE_CHANNEL: "@MOZ_UPDATE_CHANNEL@",
   MOZ_WIDGET_TOOLKIT: "@MOZ_WIDGET_TOOLKIT@",
 
+  ZEN_FIREFOX_VERSION: "@ZEN_FIREFOX_VERSION@",
+
   DEBUG_JS_MODULES: "@DEBUG_JS_MODULES@",
 
   MOZ_BING_API_CLIENTID: "@MOZ_BING_API_CLIENTID@",
