diff --git a/composer.json b/composer.json
index 45190c3..6d9cc38 100644
--- a/composer.json
+++ b/composer.json
@@ -27,6 +27,6 @@
     },
     "require-dev": {
         "composer/composer": "^1.1",
-        "phpunit/phpunit": "^5.4"
+        "phpunit/phpunit": "^4.8"
     }
 }