diff --git a/src/InputDataContainer.php b/src/InputDataContainer.php
index cc582b8..71d2b5c 100644
--- a/src/InputDataContainer.php
+++ b/src/InputDataContainer.php
@@ -34,7 +34,7 @@ public function getAttributeValue($key = null)
 
         if (count($keys) > 1) {
             $data = $this->getValueFromPath($keys, $data);
-        } elseif (isset($data[$key])) {
+        } elseif ($key && isset($data[$key])) {
             return $data[$key];
         } elseif (isset($data[$this->attributeKey])) {
             return $data[$this->attributeKey];