diff --git a/composer.json b/composer.json
index 791fef5..ec86c5b 100644
--- a/composer.json
+++ b/composer.json
@@ -25,7 +25,7 @@
         "guzzlehttp/guzzle": "^7.8"
     },
     "require-dev": {
-        "phpunit/phpunit": "^11"
+        "phpunit/phpunit": "^9"
     },
     "extra": {
         "roundcube": {