diff --git a/composer.json b/composer.json
index a94dddc..c410dc9 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
   "require-dev": {
     "friendsofphp/php-cs-fixer": "^2.16",
     "phpstan/phpstan": "^0.12",
-    "phpunit/phpunit": "^8.5"
+    "phpunit/phpunit": "^8.5 || ^9.0"
   },
   "autoload": {
     "psr-4": {