diff --git a/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-attributes-view.js b/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-attributes-view.js
index 4343a651..4a20b4f0 100644
--- a/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-attributes-view.js
+++ b/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-attributes-view.js
@@ -60,7 +60,7 @@ class IbexaCustomTagAttributesView extends View {
 
         Object.entries(attributes).forEach(([name, config]) => {
             const value = values[name] === null || values[name] === undefined || values[name] === '' ? '-' : values[name];
-            const getValueLabelMethods = window.ibexa.richText.CKEditor.customTags.getValueLabelMethods || {};
+            const getValueLabelMethods = window.ibexa.richText.CKEditor.customTags?.getValueLabelMethods || {};
             const valueLabel = getValueLabelMethods[name] && value !== '-' ? getValueLabelMethods[name](value, config) : value;
 
             children.push({
diff --git a/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-form-view.js b/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-form-view.js
index 5d081c20..300f5efa 100644
--- a/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-form-view.js
+++ b/src/bundle/Resources/public/js/CKEditor/custom-tags/ui/custom-tag-form-view.js
@@ -19,9 +19,9 @@ class IbexaCustomTagFormView extends View {
         this.saveButtonView = this.createButton('Save', null, 'ck-button-save', 'save-custom-tag');
         this.cancelButtonView = this.createButton('Cancel', null, 'ck-button-cancel', 'cancel-custom-tag');
 
-        const attributeRenderMethods = window.ibexa.richText.CKEditor.customTags.attributeRenderMethods || {};
-        const setValueMethods = window.ibexa.richText.CKEditor.customTags.setValueMethods || {};
-        const getValueMethods = window.ibexa.richText.CKEditor.customTags.getValueMethods || {};
+        const attributeRenderMethods = window.ibexa.richText.CKEditor.customTags?.attributeRenderMethods || {};
+        const setValueMethods = window.ibexa.richText.CKEditor.customTags?.setValueMethods || {};
+        const getValueMethods = window.ibexa.richText.CKEditor.customTags?.getValueMethods || {};
 
         this.attributeViews = {};
         this.attributeRenderMethods = {