diff --git a/composer.json b/composer.json
index 37f3d21f..31d420b0 100644
--- a/composer.json
+++ b/composer.json
@@ -24,7 +24,7 @@
         "container-interop/container-interop": "^1.1",
         "mongodb/mongodb": "^1.0.1",
         "php-mock/php-mock-phpunit": "^1.1.2 || ^2.0",
-        "phpunit/phpunit": "^5.7.5 || ^6.0.13",
+        "phpunit/phpunit": "^5.7.5 || >=6.0.13 <6.5.0",
         "zendframework/zend-cache": "^2.6.1",
         "zendframework/zend-coding-standard": "~1.0.0",
         "zendframework/zend-db": "^2.7",
@@ -32,9 +32,6 @@
         "zendframework/zend-servicemanager": "^2.7.5 || ^3.0.3",
         "zendframework/zend-validator": "^2.6"
     },
-    "conflict": {
-        "phpunit/phpunit": ">=6.5.0"
-    },
     "suggest": {
         "mongodb/mongodb": "If you want to use the MongoDB session save handler",
         "zendframework/zend-cache": "Zend\\Cache component",