diff --git a/includes/class-syndication-wp-xmlrpc-client.php b/includes/class-syndication-wp-xmlrpc-client.php
index b8dd678fab194645b78196c7f0ab9cabb9ff1ffe..465e84ef5af20b3f4c0e3af09655b152ec6980e6 100644
--- a/includes/class-syndication-wp-xmlrpc-client.php
+++ b/includes/class-syndication-wp-xmlrpc-client.php
@@ -224,7 +224,7 @@ class Syndication_WP_XMLRPC_Client extends WP_HTTP_IXR_Client implements Syndica
 		}
 
 		$custom_fields[] = array(
-			'key' => '_masterpost_url',
+			'key' => 'syn_source_url',
 			'value' => $post->guid,
 		);
 		return $custom_fields;