diff --git a/demos/html/ckeditor5/src/app.js b/demos/html/ckeditor5/src/app.js
index adede04ce..5108580c2 100644
--- a/demos/html/ckeditor5/src/app.js
+++ b/demos/html/ckeditor5/src/app.js
@@ -26,6 +26,7 @@ window.editor = null;
 
 // Create the CKEditor 5.
 ClassicEditor.create(document.querySelector("#editor"), {
+  licenseKey: 'GPL',
   plugins: [Essentials, Paragraph, Bold, Italic, MathType, Alignment, SourceEditing],
   toolbar: [
     "bold",
@@ -37,6 +38,7 @@ ClassicEditor.create(document.querySelector("#editor"), {
     "alignment:right",
     "sourceEditing",
   ],
+
   // language: 'de',
   // mathTypeParameters: {
   //   editorParameters: { language: 'es' }, // MathType config, including language
@@ -59,6 +61,7 @@ ClassicEditor.create(document.querySelector("#editor"), {
   });
 
 ClassicEditor.create(document.querySelector("#editor2"), {
+  licenseKey: 'GPL',
   plugins: [Essentials, Paragraph, Bold, Italic, MathType, Alignment, SourceEditing],
   toolbar: [
     "bold",