diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fc30b798..77a8a28d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ jobs:
     name: PHP ${{ matrix.php }} tests
     strategy:
       matrix:
-        php: [7.2, 7.3, 7.4]
+        php: [7.2, 7.3, 7.4, 8.0, 8.1]
     steps:
       - uses: actions/checkout@v3
       - name: Setup PHP
diff --git a/Tests/bootstrap.php b/Tests/bootstrap.php
index e31eb9ce..592a4b31 100644
--- a/Tests/bootstrap.php
+++ b/Tests/bootstrap.php
@@ -17,7 +17,7 @@
  * @property Recurly_MockClient $client
  */
 abstract class Recurly_TestCase extends TestCase {
-  function setUp() {
+  protected function setUp(): void {
     $this->client = new Recurly_MockClient();
     foreach ($this->defaultResponses() as $request) {
       call_user_func_array(array($this->client, 'addResponse'), $request);
diff --git a/composer.json b/composer.json
index e1140b12..e5bf7fec 100644
--- a/composer.json
+++ b/composer.json
@@ -7,11 +7,10 @@
     "license": "MIT",
     "authors": [],
     "require": {
-        "php": ">=5.6",
         "ext-curl": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": ">=5.7,<8"
+        "phpunit/phpunit": "^8"
     },
     "autoload": {
         "classmap": ["lib"]