Index: src/wp-admin/includes/file.php
===================================================================
--- src/wp-admin/includes/file.php	(revision 43049)
+++ src/wp-admin/includes/file.php	(working copy)
@@ -2160,7 +2160,7 @@
 
 	// Save the export file in the request.
 	update_post_meta( $request_id, '_export_file_url', $archive_url );
-	update_post_meta( $request_id, '_export_file_path', $archive_pathname );
+	update_post_meta( $request_id, '_export_file_path', wp_normalize_path( $archive_pathname ) );
 }
 
 /**