diff --git a/plugin-update-checker.php b/plugin-update-checker.php
index 0ae7e4c..2becd03 100644
--- a/plugin-update-checker.php
+++ b/plugin-update-checker.php
@@ -848,7 +848,7 @@ class PluginUpdate_1_3 {
 		$fields = self::$fields;
 		if (!empty($object->slug)) $fields = apply_filters('puc_retain_fields-'.$object->slug, $fields);
 		foreach($fields as $field){
-			if (isset($object->$field)) {
+			if (property_exists($object, $field)) {
 				$update->$field = $object->$field;
 			}
 		}
@@ -868,7 +868,7 @@ class PluginUpdate_1_3 {
 		$fields = self::$fields;
 		if (!empty($this->slug)) $fields = apply_filters('puc_retain_fields-'.$this->slug, $fields);
 		foreach($fields as $field){
-			if (isset($this->$field)) {
+			if (property_exists($this, $field)) {
 				$object->$field = $this->$field;
 			}
 		}