diff -u b/src/Normalizer/FieldItemListNormalizer.php b/src/Normalizer/FieldItemListNormalizer.php
--- b/src/Normalizer/FieldItemListNormalizer.php
+++ b/src/Normalizer/FieldItemListNormalizer.php
@@ -16,10 +16,6 @@
  */
 class FieldItemListNormalizer extends SerializerAwareNormalizer implements NormalizerInterface {
 
-  const FORMAT_FBIA = 'fbia';
-
-  const FORMAT_FBIA_RSS  = 'fbia_rss';
-
   /**
    * Renderer service.
    *
@@ -51,9 +47,14 @@
    * {@inheritdoc}
    */
   public function supportsNormalization($data, $format = NULL) {
+    $supported_formats = [
+      InstantArticleContentEntityNormalizer::FORMAT,
+      InstantArticleRssContentEntityNormalizer::FORMAT
+    ];
+
     // Only consider this normalizer if we are trying to normalize a field item
     // list into the 'fbia' format.
-    return ($format === static::FORMAT_FBIA || $format === static::FORMAT_FBIA_RSS) && $data instanceof FieldItemListInterface;
+    return in_array(($format, $supported_formats) && $data instanceof FieldItemListInterface;
   }
 
   /**