diff --git a/src/wp-admin/js/widgets/text-widgets.js b/src/wp-admin/js/widgets/text-widgets.js
index 6f057044cf..5a68516e5d 100644
--- a/src/wp-admin/js/widgets/text-widgets.js
+++ b/src/wp-admin/js/widgets/text-widgets.js
@@ -121,6 +121,9 @@ wp.textWidgets = ( function( $ ) {
 					wp.editor.remove( id );
 				}
 
+				// Adjust z-index for the customizer.
+				window.tinymce.ui.FloatPanel.zIndex = 500001;
+
 				wp.editor.initialize( id, {
 					tinymce: {
 						wpautop: true
diff --git a/src/wp-includes/js/tinymce/plugins/wordpress/plugin.js b/src/wp-includes/js/tinymce/plugins/wordpress/plugin.js
index 08e3cf78c9..d022137bc5 100644
--- a/src/wp-includes/js/tinymce/plugins/wordpress/plugin.js
+++ b/src/wp-includes/js/tinymce/plugins/wordpress/plugin.js
@@ -1,7 +1,9 @@
 /* global getUserSetting, setUserSetting */
 ( function( tinymce ) {
 // Set the minimum value for the modals z-index higher than #wpadminbar (100000)
-tinymce.ui.FloatPanel.zIndex = 100100;
+if ( tinymce.ui.FloatPanel.zIndex < 100100 ) {
+	tinymce.ui.FloatPanel.zIndex = 100100;
+}
 
 tinymce.PluginManager.add( 'wordpress', function( editor ) {
 	var wpAdvButton, style,