diff --git a/toolkit/modules/AppConstants.sys.mjs b/toolkit/modules/AppConstants.sys.mjs
index 13a523a989d1326b0f8faef9bac299738885e655..c2ff014dc553856161f6aec8014a27165819364b 100644
--- a/toolkit/modules/AppConstants.sys.mjs
+++ b/toolkit/modules/AppConstants.sys.mjs
@@ -175,6 +175,8 @@ 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@",