diff --git a/libraries/src/Installer/Adapter/FileAdapter.php b/libraries/src/Installer/Adapter/FileAdapter.php
index 72d41c529231f..92fecb775f4f2 100644
--- a/libraries/src/Installer/Adapter/FileAdapter.php
+++ b/libraries/src/Installer/Adapter/FileAdapter.php
@@ -48,6 +48,22 @@ class FileAdapter extends InstallerAdapter
      */
     protected $supportsDiscoverInstall = false;
 
+    /**
+     * List of processed folders
+     *
+     * @var    array
+     * @since  3.4
+     */
+    protected $folderList;
+
+    /**
+     * List of processed files
+     *
+     * @var    array
+     * @since  3.4
+     */
+    protected $fileList;
+
     /**
      * Method to copy the extension's base files from the `<files>` tag(s) and the manifest file
      *