--- panels_tabs.module
+++ panels_tabs.module
@@ -44,7 +44,7 @@ function panels_tabs_panels_pre_render($display, $renderer) {
     // Find out which regions are using the tabs style and add to an array
     foreach ($renderer->plugins['layout']['panels'] as $region_id => $title) {
       $settings = $renderer->display->panel_settings[$region_id];
-      if ($global_style && empty($settings['style'])) {
+      if ($global_style && (empty($settings['style']) || $settings['style'] == -1)) {
         $tabs_regions[] = $region_id;
       }
       elseif ($settings['style'] == 'tabs') {