diff --git a/site/plugins/admin/lang/pl_PL.json b/site/plugins/admin/lang/pl_PL.json
index cc8c08f5..6dd5120d 100644
--- a/site/plugins/admin/lang/pl_PL.json
+++ b/site/plugins/admin/lang/pl_PL.json
@@ -18,6 +18,7 @@
   "admin_themes": "Motywy",
   "admin_help": "Pomoc",
   "admin_getting_help": "Pomoc",
+  "admin_message_json_invalid": "Invalid JSON",
   "admin_logout": "Wyloguj",
   "admin_profile": "Profil",
   "admin_view_site": "Wyświetl stronę",