diff --git a/etc/forms/forms-d2.el b/etc/forms/forms-d2.el
index 67cdb9cd010..1b0d6426e03 100644
--- a/etc/forms/forms-d2.el
+++ b/etc/forms/forms-d2.el
@@ -1,4 +1,4 @@
-;;; forms-d2.el --- demo forms-mode
+;;; forms-d2.el --- demo forms-mode  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 1991, 1994-1997, 2001-2020 Free Software Foundation,
 ;; Inc.
diff --git a/etc/forms/forms-pass.el b/etc/forms/forms-pass.el
index 34d4548434b..0f4ab48247e 100644
--- a/etc/forms/forms-pass.el
+++ b/etc/forms/forms-pass.el
@@ -1,4 +1,4 @@
-;;; forms-pass.el --- passwd file demo for forms-mode
+;;; forms-pass.el --- passwd file demo for forms-mode  -*- lexical-binding:t -*-
 
 ;; This file is part of GNU Emacs.
 
diff --git a/lisp/emacs-lisp/edebug.el b/lisp/emacs-lisp/edebug.el
index bb7817f242c..a376067443a 100644
--- a/lisp/emacs-lisp/edebug.el
+++ b/lisp/emacs-lisp/edebug.el
@@ -1833,9 +1833,6 @@ contains a circular object."
   ;; This means nothing matched, so it is OK.
   nil) ;; So, return nothing
 
-
-(def-edebug-spec &key edebug-match-&key)
-
 (defun edebug-match-&key (cursor specs)
   ;; Following specs must look like (<name> <spec>) ...
   ;; where <name> is the name of a keyword, and spec is its spec.
@@ -2115,10 +2112,10 @@ into `edebug--cl-macrolet-defs' which is checked in `edebug-list-form-args'."
 
 (def-edebug-spec edebug-spec
   (&or
+   edebug-spec-list
    (vector &rest edebug-spec)		; matches a vector
    ("vector" &rest edebug-spec)		; matches a vector spec
    ("quote" symbolp)
-   edebug-spec-list
    stringp
    [edebug-lambda-list-keywordp &rest edebug-spec]
    [keywordp gate edebug-spec]
diff --git a/lisp/textmodes/po.el b/lisp/textmodes/po.el
index d5645e86304..29c6d3f4608 100644
--- a/lisp/textmodes/po.el
+++ b/lisp/textmodes/po.el
@@ -1,4 +1,4 @@
-;;; po.el --- basic support of PO translation files
+;;; po.el --- basic support of PO translation files  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 1995-1998, 2000-2020 Free Software Foundation, Inc.
 
diff --git a/src/fringe.c b/src/fringe.c
index d8d80bb3fe9..fc4c738dc2d 100644
--- a/src/fringe.c
+++ b/src/fringe.c
@@ -101,7 +101,7 @@ struct fringe_bitmap
   ...xx...
 */
 static unsigned short question_mark_bits[] = {
-  0x3c, 0x7e, 0x7e, 0x0c, 0x18, 0x18, 0x00, 0x18, 0x18};
+  0x3c, 0x7e, 0xc3, 0xc3, 0x0c, 0x18, 0x18, 0x00, 0x18, 0x18};
 
 /* An exclamation mark.  */
 /*
@@ -117,7 +117,7 @@ static unsigned short question_mark_bits[] = {
   ...XX...
 */
 static unsigned short exclamation_mark_bits[] = {
-  0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x00, 0x18};
+  0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x00, 0x18, 0x18};
 
 /* An arrow like this: `<-'.  */
 /*
diff --git a/src/ftfont.c b/src/ftfont.c
index 6b549c3ddf2..696f5e65341 100644
--- a/src/ftfont.c
+++ b/src/ftfont.c
@@ -346,18 +346,15 @@ struct ftfont_cache_data
 static Lisp_Object
 ftfont_lookup_cache (Lisp_Object key, enum ftfont_cache_for cache_for)
 {
-  Lisp_Object cache, val, entity;
+  Lisp_Object cache, val;
   struct ftfont_cache_data *cache_data;
 
   if (FONT_ENTITY_P (key))
     {
-      entity = key;
-      val = assq_no_quit (QCfont_entity, AREF (entity, FONT_EXTRA_INDEX));
+      val = assq_no_quit (QCfont_entity, AREF (key, FONT_EXTRA_INDEX));
       eassert (CONSP (val));
       key = XCDR (val);
     }
-  else
-    entity = Qnil;
 
   if (NILP (ft_face_cache))
     cache = Qnil;
diff --git a/src/image.c b/src/image.c
index ffe2f607e52..c8a192aaaf1 100644
--- a/src/image.c
+++ b/src/image.c
@@ -6308,14 +6308,16 @@ native_image_p (Lisp_Object object)
 static bool
 native_image_load (struct frame *f, struct image *img)
 {
+  Lisp_Object image_file = image_spec_value (img->spec, QCfile, NULL);
+
+  if (STRINGP (image_file))
+    image_file = image_find_image_file (image_file);
 
 # ifdef HAVE_NTGUI
-  return w32_load_image (f, img,
-                         image_spec_value (img->spec, QCfile, NULL),
+  return w32_load_image (f, img, image_file,
                          image_spec_value (img->spec, QCdata, NULL));
 # elif defined HAVE_NS
-  return ns_load_image (f, img,
-                        image_spec_value (img->spec, QCfile, NULL),
+  return ns_load_image (f, img, image_file,
                         image_spec_value (img->spec, QCdata, NULL));
 # else
   return 0;
diff --git a/src/w32image.c b/src/w32image.c
index 8d39a09dc7e..70b2eb29b87 100644
--- a/src/w32image.c
+++ b/src/w32image.c
@@ -414,7 +414,6 @@ w32_load_image (struct frame *f, struct image *img,
      and succeeded.  We have a valid token and GDI+ is active.  */
   if (STRINGP (spec_file))
     {
-      spec_file = ENCODE_FILE (spec_file);
       const char *fn = map_w32_filename (SSDATA (spec_file), NULL);
       wchar_t filename_w[MAX_PATH];
       filename_to_utf16 (fn, filename_w);
diff --git a/test/lisp/international/ccl-tests.el b/test/lisp/international/ccl-tests.el
index 3581cd784f0..283b2e1b32b 100644
--- a/test/lisp/international/ccl-tests.el
+++ b/test/lisp/international/ccl-tests.el
@@ -1,3 +1,5 @@
+;;; ccl-tests.el --- unit tests for ccl.el  -*- lexical-binding:t -*-
+
 ;; Copyright (C) 2018-2020 Free Software Foundation, Inc.
 
 ;; This file is part of GNU Emacs.
diff --git a/test/lisp/international/mule-util-tests.el b/test/lisp/international/mule-util-tests.el
index c571782d635..cc199bd4972 100644
--- a/test/lisp/international/mule-util-tests.el
+++ b/test/lisp/international/mule-util-tests.el
@@ -1,4 +1,4 @@
-;;; mule-util --- tests for international/mule-util.el
+;;; mule-util-tests.el --- tests for international/mule-util.el  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2002-2020 Free Software Foundation, Inc.
 
@@ -81,4 +81,4 @@
 (dotimes (i (length mule-util-test-truncate-data))
   (mule-util-test-truncate-create i))
 
-;;; mule-util.el ends here
+;;; mule-util-tests.el ends here
diff --git a/test/lisp/net/dbus-tests.el b/test/lisp/net/dbus-tests.el
index 68f69f62b56..e263c4563fe 100644
--- a/test/lisp/net/dbus-tests.el
+++ b/test/lisp/net/dbus-tests.el
@@ -1,4 +1,4 @@
-;;; dbus-tests.el --- Tests of D-Bus integration into Emacs
+;;; dbus-tests.el --- Tests of D-Bus integration into Emacs  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2013-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/net/gnutls-tests.el b/test/lisp/net/gnutls-tests.el
index c2472d844c1..07e30b64642 100644
--- a/test/lisp/net/gnutls-tests.el
+++ b/test/lisp/net/gnutls-tests.el
@@ -1,4 +1,4 @@
-;;; gnutls-tests.el --- Test suite for gnutls.el
+;;; gnutls-tests.el --- Test suite for gnutls.el  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2017-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/net/newsticker-tests.el b/test/lisp/net/newsticker-tests.el
index 1a6e11dc512..5552fa8c1a6 100644
--- a/test/lisp/net/newsticker-tests.el
+++ b/test/lisp/net/newsticker-tests.el
@@ -1,4 +1,4 @@
-;;; newsticker-testsuite.el --- Test suite for newsticker.
+;;; newsticker-tests.el --- Test suite for newsticker.  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2003-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/net/puny-tests.el b/test/lisp/net/puny-tests.el
index 9fb2ebb5469..288bc2ff6fe 100644
--- a/test/lisp/net/puny-tests.el
+++ b/test/lisp/net/puny-tests.el
@@ -1,4 +1,4 @@
-;;; puny-tests.el --- tests for net/puny.el  -*- coding: utf-8; -*-
+;;; puny-tests.el --- tests for net/puny.el  -*- coding: utf-8; lexical-binding:t -*-
 
 ;; Copyright (C) 2017-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/net/rfc2104-tests.el b/test/lisp/net/rfc2104-tests.el
index 5c1f4410934..90535898382 100644
--- a/test/lisp/net/rfc2104-tests.el
+++ b/test/lisp/net/rfc2104-tests.el
@@ -1,4 +1,4 @@
-;;; rfc2104-tests.el --- Tests of RFC2104 hashes
+;;; rfc2104-tests.el --- Tests of RFC2104 hashes  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2019-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/textmodes/mhtml-mode-tests.el b/test/lisp/textmodes/mhtml-mode-tests.el
index aa5f19efdaa..1840e8b4016 100644
--- a/test/lisp/textmodes/mhtml-mode-tests.el
+++ b/test/lisp/textmodes/mhtml-mode-tests.el
@@ -1,4 +1,4 @@
-;;; mhtml-mode-tests.el --- Tests for mhtml-mode
+;;; mhtml-mode-tests.el --- Tests for mhtml-mode  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2017-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/textmodes/po-tests.el b/test/lisp/textmodes/po-tests.el
new file mode 100644
index 00000000000..a098290ce15
--- /dev/null
+++ b/test/lisp/textmodes/po-tests.el
@@ -0,0 +1,68 @@
+;;; po-tests.el --- Tests for po.el                  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2020 Free Software Foundation, Inc.
+
+;; Author: Simen Heggestøyl <simenheg@gmail.com>
+;; Keywords:
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+
+(require 'po)
+(require 'ert)
+
+(defconst po-tests--buffer-string
+  "# Norwegian bokmål translation of the GIMP.
+# Copyright (C) 1999-2001 Free Software Foundation, Inc.
+#
+msgid \"\"
+msgstr \"\"
+\"Project-Id-Version: gimp 2.8.5\\n\"
+\"Report-Msgid-Bugs-To: https://gitlab.gnome.org/GNOME/gimp/issues\\n\"
+\"POT-Creation-Date: 2013-05-27 14:57+0200\\n\"
+\"PO-Revision-Date: 2013-05-27 15:21+0200\\n\"
+\"Language: nb\\n\"
+\"MIME-Version: 1.0\\n\"
+\"Content-Type: text/plain; charset=UTF-8\\n\"
+\"Content-Transfer-Encoding: 8bit\\n\"
+\"Plural-Forms: nplurals=2; plural=(n != 1);\\n\"
+
+#: ../desktop/gimp.desktop.in.in.h:1 ../app/about.h:26
+msgid \"GNU Image Manipulation Program\"
+msgstr \"GNU bildebehandlingsprogram\"
+")
+
+(ert-deftest po-tests-find-charset ()
+  (with-temp-buffer
+    (insert po-tests--buffer-string)
+    (should (equal (po-find-charset (cons nil (current-buffer)))
+                   "UTF-8"))))
+
+(ert-deftest po-tests-find-file-coding-system-guts ()
+  (with-temp-buffer
+    (insert po-tests--buffer-string)
+    (should (equal (po-find-file-coding-system-guts
+                    'insert-file-contents
+                    (cons "*tmp*" (current-buffer)))
+                   '(utf-8 . nil)))))
+
+(provide 'po-tests)
+;;; po-tests.el ends here
diff --git a/test/lisp/textmodes/sgml-mode-tests.el b/test/lisp/textmodes/sgml-mode-tests.el
index f0b93e24d2c..a4457307b35 100644
--- a/test/lisp/textmodes/sgml-mode-tests.el
+++ b/test/lisp/textmodes/sgml-mode-tests.el
@@ -1,4 +1,4 @@
-;;; sgml-mode-tests.el --- Tests for sgml-mode
+;;; sgml-mode-tests.el --- Tests for sgml-mode  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2015-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/url/url-auth-tests.el b/test/lisp/url/url-auth-tests.el
index c574f3d373b..d3acdef8535 100644
--- a/test/lisp/url/url-auth-tests.el
+++ b/test/lisp/url/url-auth-tests.el
@@ -1,4 +1,4 @@
-;;; url-auth-tests.el --- Test suite for url-auth.
+;;; url-auth-tests.el --- Test suite for url-auth.  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2015-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/url/url-expand-tests.el b/test/lisp/url/url-expand-tests.el
index 553bcf67bd2..6e0ce869502 100644
--- a/test/lisp/url/url-expand-tests.el
+++ b/test/lisp/url/url-expand-tests.el
@@ -1,4 +1,4 @@
-;;; url-expand-tests.el --- Test suite for relative URI/URL resolution.
+;;; url-expand-tests.el --- Test suite for relative URI/URL resolution.  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2012-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/url/url-parse-tests.el b/test/lisp/url/url-parse-tests.el
index 98e6dcb9aed..6ec46479a6f 100644
--- a/test/lisp/url/url-parse-tests.el
+++ b/test/lisp/url/url-parse-tests.el
@@ -1,4 +1,4 @@
-;;; url-parse-tests.el --- Test suite for URI/URL parsing.
+;;; url-parse-tests.el --- Test suite for URI/URL parsing.  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2012-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/url/url-tramp-tests.el b/test/lisp/url/url-tramp-tests.el
index d6f830afcf2..965b9ea0888 100644
--- a/test/lisp/url/url-tramp-tests.el
+++ b/test/lisp/url/url-tramp-tests.el
@@ -1,4 +1,4 @@
-;;; url-tramp-tests.el --- Test suite for Tramp / URL conversion.
+;;; url-tramp-tests.el --- Test suite for Tramp / URL conversion.  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2017-2020 Free Software Foundation, Inc.
 
diff --git a/test/lisp/url/url-util-tests.el b/test/lisp/url/url-util-tests.el
index fd3a8d6e108..0416331b032 100644
--- a/test/lisp/url/url-util-tests.el
+++ b/test/lisp/url/url-util-tests.el
@@ -1,4 +1,4 @@
-;;; url-util-tests.el --- Test suite for url-util.
+;;; url-util-tests.el --- Test suite for url-util.  -*- lexical-binding:t -*-
 
 ;; Copyright (C) 2012-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/charset-tests.el b/test/src/charset-tests.el
index 01a68c21a52..9a1d0a46f91 100644
--- a/test/src/charset-tests.el
+++ b/test/src/charset-tests.el
@@ -1,4 +1,4 @@
-;;; charset-tests.el --- Tests for charset.c
+;;; charset-tests.el --- Tests for charset.c -*- lexical-binding: t -*-
 
 ;; Copyright 2017-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/chartab-tests.el b/test/src/chartab-tests.el
index da320e33b51..0ddea2b338c 100644
--- a/test/src/chartab-tests.el
+++ b/test/src/chartab-tests.el
@@ -1,4 +1,4 @@
-;;; chartab-tests.el --- Tests for char-tab.c
+;;; chartab-tests.el --- Tests for char-tab.c -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2016-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/cmds-tests.el b/test/src/cmds-tests.el
index 8604d346109..e98e5784609 100644
--- a/test/src/cmds-tests.el
+++ b/test/src/cmds-tests.el
@@ -1,4 +1,4 @@
-;;; cmds-tests.el --- Testing some Emacs commands
+;;; cmds-tests.el --- Testing some Emacs commands -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/coding-tests.el b/test/src/coding-tests.el
index a741e233d39..c438ae22ce3 100644
--- a/test/src/coding-tests.el
+++ b/test/src/coding-tests.el
@@ -1,4 +1,4 @@
-;;; coding-tests.el --- tests for text encoding and decoding
+;;; coding-tests.el --- tests for text encoding and decoding -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013-2020 Free Software Foundation, Inc.
 
@@ -296,7 +296,7 @@
 ;;; decoder, not for regression testing.
 
 (defun generate-ascii-file ()
-  (dotimes (i 100000)
+  (dotimes (_i 100000)
     (insert-char ?a 80)
     (insert "\n")))
 
@@ -309,13 +309,13 @@
     (insert "\n")))
 
 (defun generate-mostly-nonascii-file ()
-  (dotimes (i 30000)
+  (dotimes (_i 30000)
     (insert-char ?a 80)
     (insert "\n"))
-  (dotimes (i 20000)
+  (dotimes (_i 20000)
     (insert-char ?À 80)
     (insert "\n"))
-  (dotimes (i 10000)
+  (dotimes (_i 10000)
     (insert-char ?あ 80)
     (insert "\n")))
 
diff --git a/test/src/decompress-tests.el b/test/src/decompress-tests.el
index 46fd26635c9..0a328396818 100644
--- a/test/src/decompress-tests.el
+++ b/test/src/decompress-tests.el
@@ -1,4 +1,4 @@
-;;; decompress-tests.el --- Test suite for decompress.
+;;; decompress-tests.el --- Test suite for decompress. -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/doc-tests.el b/test/src/doc-tests.el
index b6026e79c65..50cf0144b80 100644
--- a/test/src/doc-tests.el
+++ b/test/src/doc-tests.el
@@ -1,4 +1,4 @@
-;;; doc-tests.el --- Tests for doc.c
+;;; doc-tests.el --- Tests for doc.c -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2016-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/floatfns-tests.el b/test/src/floatfns-tests.el
index c1c2c8996a7..8c56674d4fd 100644
--- a/test/src/floatfns-tests.el
+++ b/test/src/floatfns-tests.el
@@ -1,4 +1,4 @@
-;;; floatfns-tests.el --- tests for floating point operations
+;;; floatfns-tests.el --- tests for floating point operations -*- lexical-binding: t -*-
 
 ;; Copyright 2017-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/font-tests.el b/test/src/font-tests.el
index 73c2846b032..cfc6f4c31b7 100644
--- a/test/src/font-tests.el
+++ b/test/src/font-tests.el
@@ -1,4 +1,4 @@
-;;; font-tests.el --- Test suite for font-related functions.
+;;; font-tests.el --- Test suite for font-related functions. -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2011-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/keymap-tests.el b/test/src/keymap-tests.el
index dbf0a7d1229..75f8c0f092e 100644
--- a/test/src/keymap-tests.el
+++ b/test/src/keymap-tests.el
@@ -1,4 +1,4 @@
-;;; keymap-tests.el --- Test suite for src/keymap.c
+;;; keymap-tests.el --- Test suite for src/keymap.c -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2015-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/process-tests.el b/test/src/process-tests.el
index 66a76fd33b8..748afe41d2c 100644
--- a/test/src/process-tests.el
+++ b/test/src/process-tests.el
@@ -1,4 +1,4 @@
-;;; process-tests.el --- Testing the process facilities
+;;; process-tests.el --- Testing the process facilities -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2013-2020 Free Software Foundation, Inc.
 
@@ -33,7 +33,7 @@
   (let ((proc (start-process "test" nil "bash" "-c" "exit 20"))
 	(sentinel-called nil)
 	(start-time (float-time)))
-    (set-process-sentinel proc (lambda (proc msg)
+    (set-process-sentinel proc (lambda (_proc _msg)
 				 (setq sentinel-called t)))
     (while (not (or sentinel-called
 		    (> (- (float-time) start-time)
@@ -88,7 +88,7 @@
 			     :stderr stderr-buffer))
 	 (sentinel-called nil)
 	 (start-time (float-time)))
-    (set-process-sentinel proc (lambda (proc msg)
+    (set-process-sentinel proc (lambda (_proc _msg)
 				 (setq sentinel-called t)))
     (while (not (or sentinel-called
 		    (> (- (float-time) start-time)
@@ -120,13 +120,13 @@
 						    "exit 20"))
 			     :stderr stderr-proc))
 	 (start-time (float-time)))
-    (set-process-filter proc (lambda (proc input)
+    (set-process-filter proc (lambda (_proc input)
 			       (push input stdout-output)))
-    (set-process-sentinel proc (lambda (proc msg)
+    (set-process-sentinel proc (lambda (_proc _msg)
 				 (setq sentinel-called t)))
-    (set-process-filter stderr-proc (lambda (proc input)
+    (set-process-filter stderr-proc (lambda (_proc input)
 				      (push input stderr-output)))
-    (set-process-sentinel stderr-proc (lambda (proc input)
+    (set-process-sentinel stderr-proc (lambda (_proc _input)
 					(setq stderr-sentinel-called t)))
     (while (not (or sentinel-called
 		    (> (- (float-time) start-time)
diff --git a/test/src/textprop-tests.el b/test/src/textprop-tests.el
index 7333444df0b..365d2c7a7b7 100644
--- a/test/src/textprop-tests.el
+++ b/test/src/textprop-tests.el
@@ -1,4 +1,4 @@
-;;; textprop-tests.el --- Test suite for text properties.
+;;; textprop-tests.el --- Test suite for text properties. -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2015-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/thread-tests.el b/test/src/thread-tests.el
index 5d85fc74e50..df34a2b66eb 100644
--- a/test/src/thread-tests.el
+++ b/test/src/thread-tests.el
@@ -1,4 +1,4 @@
-;;; threads.el --- tests for threads.
+;;; threads.el --- tests for threads. -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2012-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/timefns-tests.el b/test/src/timefns-tests.el
index b24d44335e5..51dd1d1aeb5 100644
--- a/test/src/timefns-tests.el
+++ b/test/src/timefns-tests.el
@@ -1,4 +1,4 @@
-;;; timefns-tests.el -- tests for timefns.c
+;;; timefns-tests.el -- tests for timefns.c -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2016-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/undo-tests.el b/test/src/undo-tests.el
index 995e4365e12..13335a9bb10 100644
--- a/test/src/undo-tests.el
+++ b/test/src/undo-tests.el
@@ -1,4 +1,4 @@
-;;; undo-tests.el --- Tests of primitive-undo
+;;; undo-tests.el --- Tests of primitive-undo -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2012-2020 Free Software Foundation, Inc.
 
diff --git a/test/src/xml-tests.el b/test/src/xml-tests.el
index 02a52e9115d..d758c8868cf 100644
--- a/test/src/xml-tests.el
+++ b/test/src/xml-tests.el
@@ -1,4 +1,4 @@
-;;; libxml-parse-tests.el --- Test suite for libxml parsing.
+;;; xml-tests.el --- Test suite for libxml parsing. -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2014-2020 Free Software Foundation, Inc.