diff --git a/pkgs/applications/networking/browsers/firefox-bin/default.nix b/pkgs/applications/networking/browsers/firefox-bin/default.nix
index fab98ad2e2b..4262609c66b 100644
--- a/pkgs/applications/networking/browsers/firefox-bin/default.nix
+++ b/pkgs/applications/networking/browsers/firefox-bin/default.nix
@@ -50,6 +50,7 @@
 , gnupg
 , ffmpeg
 , runtimeShell
+, systemLocale ? config.i18n.defaultLocale or "en-US"
 }:
 
 let
@@ -69,8 +70,6 @@ let
   sourceMatches = locale: source:
       (isPrefixOf source.locale locale) && source.arch == arch;
 
-  systemLocale = config.i18n.defaultLocale or "en-US";
-
   policies = {
     DisableAppUpdate = true;
   };