diff --git a/composer.json b/composer.json
index c733d77..0a0e210 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
   },
 
   "require-dev": {
-    "phpunit/phpunit": "5.3.*",
+    "phpunit/phpunit": "5..4*",
     "phpdocumentor/phpdocumentor": "2.8.*",
     "squizlabs/php_codesniffer": "2.*"
   }