diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 0bb6f3c..f65c2f2 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -14,18 +14,16 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        emacs_version: ['24.4', '24.5',
-                        '25.1', '25.2', '25.3',
-                        '26.1', '26.2', '26.3',
-                        '27.1', '27.2',
+        emacs_version: ['27.1', '27.2',
                         '28.1', '28.2',
-                        '29.1',
+                        '29.1', '29.2', '29.3', '29.4',
+                        '30.1',
                         'snapshot']
         include:
           - os: macos-latest
-            emacs_version: '29.1'
+            emacs_version: '30.1'
           - os: windows-latest
-            emacs_version: '29.1'
+            emacs_version: '30.1'
 
     steps:
     - name: Set up Emacs
diff --git a/test/flycheck-eldev-test.el b/test/flycheck-eldev-test.el
index ba57b6d..448c478 100644
--- a/test/flycheck-eldev-test.el
+++ b/test/flycheck-eldev-test.el
@@ -1,3 +1,4 @@
+;; -*- lexical-binding: t; -*-
 (require 'flycheck-eldev)
 (require 'ert)
 (require 'dash)
@@ -148,7 +149,7 @@
 ;; When checking the faulty `Eldev-local', we must not use it for initialization.
 (ert-deftest flycheck-eldev-faulty-eldev-local-2 ()
   (flycheck-eldev--test-with-temp-file "project-a/Eldev-local"
-      (insert "this-variable-certainly-doesnt-exist")
+      (insert ";; -*- lexical-binding: t; -*-\nthis-variable-certainly-doesnt-exist")
     (flycheck-eldev--test "project-a/Eldev-local"
       (flycheck-eldev--test-recheck)
       (flycheck-eldev--test-expect-errors '(:matches "this-variable-certainly-doesnt-exist")))))
@@ -156,7 +157,7 @@
 ;; Test that `flycheck-eldev' really works on Eldev files if those are byte-compilable.
 (ert-deftest flycheck-eldev-suspicious-eldev-local-1 ()
   (flycheck-eldev--test-with-temp-file "project-a/Eldev-local"
-      (insert "(defun just-for-testing () (function-with-this-name-certainly-doesnt-exist))")
+      (insert ";; -*- lexical-binding: t; -*-\n(defun just-for-testing () (function-with-this-name-certainly-doesnt-exist))")
     (flycheck-eldev--test "project-a/Eldev-local"
       (flycheck-eldev--test-recheck)
       (flycheck-eldev--test-expect-errors '(:matches "function-with-this-name-certainly-doesnt-exist")))))
diff --git a/test/project-a/project-a.el b/test/project-a/project-a.el
index 3b6395c..b3d426b 100644
--- a/test/project-a/project-a.el
+++ b/test/project-a/project-a.el
@@ -1,4 +1,4 @@
-;;; project-a.el --- Test project with one dependency
+;;; project-a.el --- Test project with one dependency -*- lexical-binding: t; -*-
 
 ;; Version: 1.0
 ;; Homepage: https://example.com/
diff --git a/test/project-a/test/project-a.el b/test/project-a/test/project-a.el
index 5d6beae..0601298 100644
--- a/test/project-a/test/project-a.el
+++ b/test/project-a/test/project-a.el
@@ -1,3 +1,4 @@
+;; -*- lexical-binding: t; -*-
 ;; Using loading root to test that `flycheck-eldev' handles this too.
 (require 'test-util)