diff --git a/composer.json b/composer.json
index e4a6d46..9988554 100644
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,7 @@
         "ext-parallel": "*"
     },
     "require-dev": {
-        "wyrihaximus/async-test-utilities": "^5 || ^7.2"
+        "wyrihaximus/async-test-utilities": "^5 || ^7.2 || ^9.0"
     },
     "config": {
         "allow-plugins": {