diff --git a/model/Versioned.php b/model/Versioned.php
index dc9a62500..7b6924c1f 100644
--- a/model/Versioned.php
+++ b/model/Versioned.php
@@ -107,7 +107,7 @@ class Versioned extends DataExtension {
 		'Version' => 'Int'
 	);
 
-	static function add_to_class($class, $extensionClass, $args) {
+	static function add_to_class($class, $extensionClass, $args = null) {
 		Config::inst()->update($class, 'has_many', array('Versions' => $class));
 		parent::add_to_class($class, $extensionClass, $args);
 	}