diff --git a/src/wp-admin/js/customize-controls.js b/src/wp-admin/js/customize-controls.js
index 4e3da867a7..ed75ba3df1 100644
--- a/src/wp-admin/js/customize-controls.js
+++ b/src/wp-admin/js/customize-controls.js
@@ -9252,8 +9252,8 @@
 		api.bind( 'change', startAutosaving );
 
 		// Make sure TinyMCE dialogs appear above Customizer UI.
-		$( document ).one( 'wp-before-tinymce-init', function() {
-			if ( ! window.tinymce.ui.FloatPanel.zIndex || window.tinymce.ui.FloatPanel.zIndex < 500001 ) {
+		$( document ).one( 'tinymce-editor-setup', function() {
+			if ( window.tinymce.ui.FloatPanel && ( ! window.tinymce.ui.FloatPanel.zIndex || window.tinymce.ui.FloatPanel.zIndex < 500001 ) ) {
 				window.tinymce.ui.FloatPanel.zIndex = 500001;
 			}
 		} );