diff --git a/plugins/display_renderers/panels_renderer_editor.class.php b/plugins/display_renderers/panels_renderer_editor.class.php
index 0ca2146..5d6fe64 100644
--- a/plugins/display_renderers/panels_renderer_editor.class.php
+++ b/plugins/display_renderers/panels_renderer_editor.class.php
@@ -1696,6 +1696,7 @@ function panels_edit_style_settings_form(&$form_state) {
  * Validate style settings.
  */
 function panels_edit_style_settings_form_validate($form, &$form_state) {
+  ctools_include('plugins', 'panels');
   $name = $form_state['type'] == 'pane' ? 'pane settings form validate' : 'settings form validate';
   if ($function = panels_plugin_get_function('styles', $form_state['style'], $name)) {
     $function($form, $form_state['values']['settings'], $form_state);