diff --git a/src/Normalizer/ContentEntityNormalizer.php b/src/Normalizer/ContentEntityNormalizer.php
index 5b06725..55ffa10 100644
--- a/src/Normalizer/ContentEntityNormalizer.php
+++ b/src/Normalizer/ContentEntityNormalizer.php
@@ -195,7 +195,7 @@ public function normalize($entity, $format = NULL, array $context = []): array|b
   /**
    * {@inheritdoc}
    */
-  public function denormalize($data, $class, $format = NULL, array $context = []) {
+  public function denormalize(mixed $data, string $class, ?string $format = NULL, array $context = []) : mixed {
 
     // Get type, necessary for determining which bundle to create.
     if (!isset($data['_links']['type'])) {