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
@@ -62,7 +62,7 @@
    * Implements \Symfony\Component\Serializer\Encoder\EncoderInterface::decode().
    */
   public function decode($data, $format, array $context = array()){
-    return $this->baseEncoder->decode($data, $format, $context);
+    return $this->baseEncoder->decode($data, $format, $context) + array('@xmlns' => 'x-schema:pgn.xdr');
   }
 
   /**
diff -u b/lib/Drupal/pgn/Tests/XmlEncoderUnitTest.php b/lib/Drupal/pgn/Tests/XmlEncoderUnitTest.php
--- b/lib/Drupal/pgn/Tests/XmlEncoderUnitTest.php
+++ b/lib/Drupal/pgn/Tests/XmlEncoderUnitTest.php
@@ -10027,7 +10027,6 @@
     $decoded = $encoder->decode($this->pgnxml, 'pgnxml');
 
     $expected = $this->normalized;
-    unset($expected['@xmlns']);
 
     $this->assertEqual($expected, $decoded, 'Decoded PGNXML is equal to expected PGN data.');