diff --git a/composer.json b/composer.json
index 983de4cb7fe47580643717b69cbf26bba47e7997..5a359d76edb528a5270778547770b0edc7ac3c30 100644
--- a/composer.json
+++ b/composer.json
@@ -41,7 +41,7 @@
         "mikey179/vfsStream": "^1.6",
         "phpmd/phpmd": "^2.6.0",
         "phpspec/prophecy": "^1.8",
-        "phpunit/phpunit": "4 - 5",
+        "phpunit/phpunit": "^6.5",
         "squizlabs/php_codesniffer": "^3.3",
         "symfony/css-selector": "^3.4",
         "symfony/debug": "^3.4",