diff --git a/core/modules/views/views.post_update.php b/core/modules/views/views.post_update.php
index 075dd21..1370627 100644
--- a/core/modules/views/views.post_update.php
+++ b/core/modules/views/views.post_update.php
@@ -213,7 +213,7 @@ function views_post_update_admin_theme() {
       // Deal only with page displays.
       if ($display['display_plugin'] == 'page') {
         $trail = "display.$display_id.display_options.admin_theme";
-        $view->set($trail, NULL)->save();
+        $view->set($trail, $view->get($trail))->save();
       }
     }
   }