diff --git a/wp-admin/upgrade-functions.php b/wp-admin/upgrade-functions.php
index 26fe29c53b..960b0f54b8 100644
--- a/wp-admin/upgrade-functions.php
+++ b/wp-admin/upgrade-functions.php
@@ -636,6 +636,7 @@ function make_site_theme() {
 		return false;
 	}
 
+	umask(0);
 	if (! mkdir($site_dir, 0777)) {
 		return false;
 	}