diff --git a/composer.json b/composer.json
index 72cc842..e52b0af 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,7 @@
     "khs1994/curl": "~18.06.0"
   },
   "require-dev": {
-    "phpunit/phpunit": "^9.0"
+    "phpunit/phpunit": "9.3.7"
   },
   "config": {
     "optimize-autoloader": true,