diff --git a/app/assets/javascripts/activeadmin/quill_editor_input.js b/app/assets/javascripts/activeadmin/quill_editor_input.js
index 7497a37..87a5d3d 100644
--- a/app/assets/javascripts/activeadmin/quill_editor_input.js
+++ b/app/assets/javascripts/activeadmin/quill_editor_input.js
@@ -1,4 +1,6 @@
 (function () {
+  'use strict'
+
   // --- functions ---------------------------------------------------------------
   function initQuillEditors() {
     let default_theme = 'snow'