Index: src/wp-admin/includes/class-theme-upgrader.php
===================================================================
--- src/wp-admin/includes/class-theme-upgrader.php	(revision 48684)
+++ src/wp-admin/includes/class-theme-upgrader.php	(working copy)
@@ -248,7 +248,7 @@
 			array(
 				'package'           => $package,
 				'destination'       => get_theme_root(),
-				'clear_destination' => $args['overwrite_package'],
+				'clear_destination' => $parsed_args['overwrite_package'],
 				'clear_working'     => true,
 				'hook_extra'        => array(
 					'type'   => 'theme',