diff --git a/composer.json b/composer.json
index c6d7626..2bb7869 100644
--- a/composer.json
+++ b/composer.json
@@ -30,6 +30,6 @@
     },
     "require-dev": {
         "composer/composer": "^1.1",
-        "phpunit/phpunit": "^4.8"
+        "phpunit/phpunit": "^5.3"
     }
 }