diff --git a/composer.json b/composer.json
index 6a53e1aa..19b804ac 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
         "symfony/web-profiler-bundle": "3.1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "4.x|5.x",
+        "phpunit/phpunit": "4.x|5.x|6.x",
         "symfony/browser-kit": "^4.0",
         "symfony/css-selector": "^4.0",
         "symfony/debug-bundle": "^4.0",