diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 1cc308f..25bb886 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -6,19 +6,19 @@ on:
 
 jobs:
   linux_tests:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     if: "!contains(github.event.head_commit.message, '[skip ci]') && !contains(github.event.head_commit.message, '[ci skip]')"
 
     strategy:
       fail-fast: true
       matrix:
-        php: [5.4, 5.5, 5.6, 7.0, 7.1, 7.2, 7.3, 7.4, 8.0, 8.1, 8.2, 8.3]
+        php: ['5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3']
 
     name: PHP ${{ matrix.php }}/Linux
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
 
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -31,10 +31,6 @@ jobs:
       - name: Setup problem matchers
         run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
 
-      - name: Fix PHPUnit for PHP8
-        run: composer config platform.php 7.4
-        if: matrix.php >= 8
-
       - name: Install dependencies
         run: composer install --prefer-dist --no-interaction --no-progress