diff --git a/composer.json b/composer.json
index 0d36e89..a560914 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
         "phpstan/phpstan": "^0.12",
         "phpstan/phpstan-mockery": "^0.12",
         "phpstan/phpstan-phpunit": "^0.12",
-        "phpunit/phpunit": "^8.0",
+        "phpunit/phpunit": "^8.0 || ^9.0",
         "roave/security-advisories": "dev-master",
         "sensiolabs-de/deptrac-shim": "^0.12.0",
         "symplify/easy-coding-standard": "8.3.*",