diff --git a/core/lib/Drupal/Core/Theme/Registry.php b/core/lib/Drupal/Core/Theme/Registry.php
index 094780a10e..46be6b9b49 100644
--- a/core/lib/Drupal/Core/Theme/Registry.php
+++ b/core/lib/Drupal/Core/Theme/Registry.php
@@ -470,14 +470,12 @@ protected function processExtension(array &$cache, $name, $type, $theme, $path)
         }
 
         if (isset($cache[$hook]['includes'])) {
-          $result[$hook]['includes'] = $cache[$hook]['includes'];
+          throw new \Exception();
         }
 
         // Load the includes, as they may contain preprocess functions.
         if (isset($info['includes'])) {
-          foreach ($info['includes'] as $include_file) {
-            include_once $this->root . '/' . $include_file;
-          }
+          throw new \Exception();
         }
 
         // If the theme implementation defines a file, then also use the path