diff --git a/core/libs/package-build-badges.el b/core/libs/package-build-badges.el
index 0a4beb316..bcc3cdff1 100644
--- a/core/libs/package-build-badges.el
+++ b/core/libs/package-build-badges.el
@@ -1,8 +1,8 @@
 ;;; package-build-badges.el --- Create batches for packages  -*- lexical-binding:t; coding:utf-8 -*-
 
-;; Copyright (C) 2011-2022 Donald Ephraim Curtis
-;; Copyright (C) 2012-2022 Steve Purcell
-;; Copyright (C) 2018-2022 Jonas Bernoulli
+;; Copyright (C) 2011-2023 Donald Ephraim Curtis
+;; Copyright (C) 2012-2023 Steve Purcell
+;; Copyright (C) 2018-2023 Jonas Bernoulli
 ;; Copyright (C) 2009 Phil Hagelberg
 
 ;; Author: Donald Ephraim Curtis <dcurtis@milkbox.net>
diff --git a/core/libs/package-build.el b/core/libs/package-build.el
index 6721a8087..5c8c3eddc 100644
--- a/core/libs/package-build.el
+++ b/core/libs/package-build.el
@@ -1,8 +1,8 @@
 ;;; package-build.el --- Tools for assembling a package archive  -*- lexical-binding:t; coding:utf-8 -*-
 
-;; Copyright (C) 2011-2022 Donald Ephraim Curtis
-;; Copyright (C) 2012-2022 Steve Purcell
-;; Copyright (C) 2016-2022 Jonas Bernoulli
+;; Copyright (C) 2011-2023 Donald Ephraim Curtis
+;; Copyright (C) 2012-2023 Steve Purcell
+;; Copyright (C) 2016-2023 Jonas Bernoulli
 ;; Copyright (C) 2009 Phil Hagelberg
 
 ;; Author: Donald Ephraim Curtis <dcurtis@milkbox.net>
@@ -13,7 +13,7 @@
 ;; Keywords: maint tools
 
 ;; Package-Version: 4.0.0.50-git
-;; Package-Requires: ((emacs "25.1"))
+;; Package-Requires: ((emacs "26.1"))
 
 ;; SPDX-License-Identifier: GPL-3.0-or-later
 
@@ -830,6 +830,7 @@ FILES is a list of (SOURCE . DEST) relative filepath pairs."
                 ((and `(,dir . ,globs)
                       (guard (stringp dir))
                       (guard (cl-every #'stringp globs)))
+                 dir ; Silence byte-compiler of Emacs < 28.1.
                  (mapcan #'toargs globs))))
             (let ((spec (or (oref rcp files) package-build-default-files-spec)))
               (if (eq (car spec) :defaults)
diff --git a/core/libs/package-recipe-mode.el b/core/libs/package-recipe-mode.el
index 05e1afee8..512937a51 100644
--- a/core/libs/package-recipe-mode.el
+++ b/core/libs/package-recipe-mode.el
@@ -1,8 +1,8 @@
 ;;; package-recipe-mode.el --- Minor mode for editing package recipes  -*- lexical-binding:t; coding:utf-8 -*-
 
-;; Copyright (C) 2011-2022 Donald Ephraim Curtis
-;; Copyright (C) 2012-2022 Steve Purcell
-;; Copyright (C) 2016-2022 Jonas Bernoulli
+;; Copyright (C) 2011-2023 Donald Ephraim Curtis
+;; Copyright (C) 2012-2023 Steve Purcell
+;; Copyright (C) 2016-2023 Jonas Bernoulli
 ;; Copyright (C) 2009 Phil Hagelberg
 
 ;; Author: Donald Ephraim Curtis <dcurtis@milkbox.net>
diff --git a/core/libs/package-recipe.el b/core/libs/package-recipe.el
index 17a47adaa..fddc96557 100644
--- a/core/libs/package-recipe.el
+++ b/core/libs/package-recipe.el
@@ -1,6 +1,6 @@
 ;;; package-recipe.el --- Package recipes as EIEIO objects  -*- lexical-binding:t; coding:utf-8 -*-
 
-;; Copyright (C) 2018-2022 Jonas Bernoulli
+;; Copyright (C) 2018-2023 Jonas Bernoulli
 
 ;; Author: Jonas Bernoulli <jonas@bernoul.li>
 ;; Homepage: https://github.com/melpa/package-build
@@ -28,6 +28,7 @@
 ;;; Code:
 
 (require 'eieio)
+(require 'subr-x)
 (require 'url-parse)
 
 (defvar package-build-use-git-remote-hg)