diff -u b/lib/Drupal/pgn/Serializer/Encoder/XmlEncoder.php b/lib/Drupal/pgn/Serializer/Encoder/XmlEncoder.php
--- b/lib/Drupal/pgn/Serializer/Encoder/XmlEncoder.php
+++ b/lib/Drupal/pgn/Serializer/Encoder/XmlEncoder.php
@@ -37,7 +37,7 @@
    * Constucts the XmlEncoder object, creating a BaseXmlEncoder also if needed.
    */
   public function __construct(BaseXmlEncoder $base_xml_encoder = NULL) {
-    $this->baseEncoder = $base_xml_encoder ?: new BaseXmlEncoder();
+    $this->baseEncoder = $base_xml_encoder === NULL ? new BaseXmlEncoder() : $base_xml_encoder;
   }
 
   /**