diff --git a/composer.json b/composer.json
index bf587dd6..1e151954 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
         "friendsofphp/php-cs-fixer": "^2.7",
         "vimeo/psalm":"^1.0",
         "jakub-onderka/php-parallel-lint": "^1.0",
-        "phpunit/phpunit": "^5.7",
+        "phpunit/phpunit": "^6.0",
         "zendframework/zendframework1": "^1.12.0"
     }