Index: src/wp-admin/includes/file.php
===================================================================
--- src/wp-admin/includes/file.php	(revision 43507)
+++ src/wp-admin/includes/file.php	(working copy)
@@ -2151,7 +2151,7 @@
 
 	$zip = new ZipArchive;
 	if ( true === $zip->open( $archive_pathname, ZipArchive::CREATE ) ) {
-		if ( ! $zip->addFile( $html_report_pathname, 'index.html' ) ) {
+		if ( ! $zip->addFile( $html_report_pathname, $html_report_filename ) ) {
 			$error = __( 'Unable to add data to export file.' );
 		}