diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index c512b9d..4738a3a 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -10,23 +10,23 @@ on:
 
 jobs:
   run:
-    runs-on: ubuntu-16.04
+    runs-on: ubuntu-latest
 
     strategy:
       matrix:
-        php: [7.1, 7.2, 7.3, 7.4]
+        php-versions: [7.1, 7.2, 7.3, 7.4]
         include:
           - php-versions: "8.0"
             dependencies: "highest"
             composer-options: "--ignore-platform-req=php"
 
-    name: PHP ${{ matrix.php }}
+    name: PHP ${{ matrix.php-versions }}
 
     steps:
       - uses: actions/checkout@v2
       - uses: shivammathur/setup-php@v2
         with:
-          php-version: ${{ matrix.php }}
+          php-version: ${{ matrix.php-versions }}
           coverage: xdebug
           tools: composer:v2
       - name: Install dependencies
diff --git a/composer.json b/composer.json
index 014e8c3..55a1b5a 100644
--- a/composer.json
+++ b/composer.json
@@ -46,7 +46,8 @@
     "psr/log": "^1.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^7.0 || ^9.3"
+    "phpunit/phpunit": "^7.0",
+    "yoast/phpunit-polyfills": "^0.2.0"
   },
   "suggest": {
     "ext-soap": "Required if you need the Tradeability API of UPS"