diff --git a/composer.json b/composer.json
index 54f305e..ec34372 100644
--- a/composer.json
+++ b/composer.json
@@ -5,6 +5,7 @@
     },
     "require-dev": {
       "mikey179/vfsStream": "*",
-		  "phpunit/phpunit": "*"
+		  "phpunit/phpunit": "*",
+		  "phpunit/php-invoker": ">=1.1.0,<1.2.0"
 		}
 }
\ No newline at end of file