diff --git a/composer.json b/composer.json
index e5d71ee..16e1279 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
     },
     "require-dev": {
         "graham-campbell/analyzer": "^2.0",
-        "graham-campbell/testbench": "^4.0",
+        "graham-campbell/testbench": "^4.0|^5.0",
         "phpunit/phpunit": "^6.5"
     },
     "autoload": {