diff --git a/composer.json b/composer.json
index b34dc32..9068f1c 100644
--- a/composer.json
+++ b/composer.json
@@ -37,11 +37,15 @@
     "plugin-modifies-downloads": true
   },
   "config": {
+    "platform": {
+        "php": "8.0.0"
+    },
+    "platform-check": true,
     "allow-plugins": {
       "topfloor/composer-cleanup-vcs-dirs": false
     }
   },
   "require-dev": {
-    "phpunit/phpunit": "^10.0"
+    "phpunit/phpunit": "^9.6"
   }
 }