diff --git a/src/Utility/WebformDialogHelper.php b/src/Utility/WebformDialogHelper.php
index 299dd8c..8034273 100644
--- a/src/Utility/WebformDialogHelper.php
+++ b/src/Utility/WebformDialogHelper.php
@@ -3,7 +3,6 @@
 namespace Drupal\webform\Utility;
 
 use Drupal\Component\Serialization\Json;
-use Drupal\Core\EventSubscriber\MainContentViewSubscriber;
 
 /**
  * Helper class for dialog methods.
@@ -31,11 +30,13 @@ class WebformDialogHelper {
       return self::$offCanvasTriggerName;
     }
 
-    if (file_exists(drupal_get_path('module', 'outside_in') .'/css/off-canvas.css')) {
-      self::$offCanvasTriggerName = 'off_canvas';
+    $main_content_renderers = \Drupal::getContainer()->getParameter('main_content_renderers');
+
+    if (isset($main_content_renderers['drupal_dialog_offcanvas'])) {
+      self::$offCanvasTriggerName = 'offcanvas';
     }
     else {
-      self::$offCanvasTriggerName = 'offcanvas';
+      self::$offCanvasTriggerName = 'off_canvas';
     }
 
     return self::$offCanvasTriggerName;
@@ -90,6 +91,7 @@ class WebformDialogHelper {
           'data-dialog-renderer' => self::getOffCanvasTriggerName(),
           'data-dialog-options' => Json::encode([
             'width' => ($width > 480) ? 480 : $width,
+            'dialogClass' => 'ui-dialog-outside-in',
           ]),
         ];
       }