diff --git a/.github/workflows/phpunit.yml b/.github/workflows/phpunit.yml
index d21210a..78041a6 100644
--- a/.github/workflows/phpunit.yml
+++ b/.github/workflows/phpunit.yml
@@ -9,10 +9,10 @@ on:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
-        php-versions: ['7.2', '7.3', '7.4', '8.0']
+        php-versions: ['7.3', '7.4', '8.0', '8.1']
 
     name: PHPUnit ${{ matrix.php-versions }}