diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6a011db..cd053af 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -34,7 +34,7 @@ jobs:
     - name: Install ancient PHPUnit
       run: composer require --dev --ignore-platform-reqs phpunit/phpunit "4.8.36"
 
-    - name: Install depedencies
+    - name: Install dependencies
       run: composer update --no-interaction
 
     - name: Build for PHP 5.5
@@ -72,7 +72,7 @@ jobs:
       with:
         submodules: recursive
 
-    - name: Install depedencies
+    - name: Install dependencies
       run: composer update --no-interaction
 
     - name: Run tests
@@ -138,6 +138,18 @@ jobs:
       matrix:
         version: [10.15]
     steps:
+      # Force PHP to 8.0
+      # Doing this because tests fail in PHP 8.1 (default on macos Github Runner as of Dec 2021)
+      # due to the old version of PHPUnit we're using.
+      # We're using an old PHPUnit because it's compatible our min supported PHP 5.5.
+      # Quick fix is to force PHP version back to 8.0, which can still run our tests without error.
+      # A real solution is to get our tests working on all PHP versions
+      # (maybe don't use PHPUnit, maybe raise our min supported PHP version so we can upgrade,
+      # or maybe use PHPUnit-Polyfills so we can use a modern PHPUnit with old PHP)
+      - name: Setup PHP 8.0
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.0'
       - name: Build PHP 8 extension and test
         run: |
           python3 -c "from urllib.request import urlretrieve; urlretrieve('${{ env.BUILDER_HOST }}/${{ env.BUILDER_SOURCE }}/${{ env.BUILDER_VERSION }}/builder.pyz?run=${{ env.RUN }}', 'builder')"
diff --git a/composer.json b/composer.json
index 4b96140..7294446 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
         "php": ">=5.5"
     },
     "require-dev": {
-        "phpunit/phpunit":"^4.8.35|^5.4.3"
+        "phpunit/phpunit":"^4.8.35|^5.6.3"
     },
     "autoload": {
         "classmap": [