diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
index e7d4609..1ece209 100644
--- a/.github/workflows/unit-tests.yml
+++ b/.github/workflows/unit-tests.yml
@@ -73,8 +73,13 @@ jobs:
           coverage: none
           tools: composer, phpunit
 
+      - name: Validate composer.json and composer.lock
+        run: composer validate
+
       - name: Install dependencies
-        run: composer install --prefer-dist --no-progress
+        run: |
+          composer update --no-interaction --prefer-dist
+          composer install --prefer-dist --no-progress
 
       - name: Install WordPress Test Suite
         env:
diff --git a/composer.json b/composer.json
index aa751d9..a28b648 100644
--- a/composer.json
+++ b/composer.json
@@ -28,7 +28,7 @@
         "dealerdirect/phpcodesniffer-composer-installer": "^1",
         "phpcompatibility/phpcompatibility-wp": "^2",
         "yoast/phpunit-polyfills": "^3",
-        "phpunit/phpunit": "^5.7.21 || ^6.5 || ^7.5 || ^8.5"
+        "phpunit/phpunit": "^7.5 || ^8.5"
     },
     "config": {
         "allow-plugins": {