diff --git a/lib/recurly/traits/xml_doc.php b/lib/recurly/traits/xml_doc.php
index 6f346479..683dd268 100644
--- a/lib/recurly/traits/xml_doc.php
+++ b/lib/recurly/traits/xml_doc.php
@@ -66,7 +66,7 @@ public function getValues()
   public function setValues($values)
   {
     foreach($values as $key => $value) {
-      $this->_values[$key] = $value;
+      $this->$key = $value;
     }
     return $this;
   }