diff --git a/.github/workflows/coveralls.yml b/.github/workflows/coveralls.yml
index 6f356f7..2886792 100644
--- a/.github/workflows/coveralls.yml
+++ b/.github/workflows/coveralls.yml
@@ -32,6 +32,10 @@ jobs:
           extensions: dom, curl, libxml, mbstring, zip, pcntl, sqlite3, pdo_sqlite, bcmath, fileinfo
           coverage: xdebug
 
+      - name: Install PHPUnit
+        run: |
+          composer require "phpunit/phpunit:9.x" --no-interaction --no-update
+
       - name: Install dependencies
         uses: "ramsey/composer-install@v1"
         with: