diff --git a/composer.json b/composer.json
index 73ee8bf..07586f0 100644
--- a/composer.json
+++ b/composer.json
@@ -32,7 +32,8 @@
     },
     "require-dev": {
         "phpunit/phpunit": "^9.5",
-        "react/socket": "^1.3"
+        "react/socket": "^1.3",
+        "guzzlehttp/psr7": "^2.7"
     },
     "scripts": {
         "abtest-client": "ABTEST=client && sh tests/ab/run_ab_tests.sh",