diff --git a/src/Normalizer/EntityNormalizerTrait.php b/src/Normalizer/EntityNormalizerTrait.php
index 1cd343d5d3aefcd524dc5bba30b30710c44f6062..4ebc6d1a11110b0834c3b4d75ba5430e86f4fea0 100644
--- a/src/Normalizer/EntityNormalizerTrait.php
+++ b/src/Normalizer/EntityNormalizerTrait.php
@@ -21,6 +21,11 @@ trait EntityNormalizerTrait {
    *   The modified input data.
    */
   protected function prepareInput(array $data, ResourceType $resource_type) {
+    /** @var \Drupal\Core\Field\FieldStorageDefinitionInterface[] $field_storage_definitions */
+    $field_storage_definitions = \Drupal::service('entity_field.manager')
+      ->getFieldStorageDefinitions(
+        $resource_type->getEntityTypeId()
+      );
     $data_internal = [];
     /** @var \Drupal\jsonapi_extras\ResourceType\ConfigurableResourceType $resource_type */
     // Translate the public fields into the entity fields.
@@ -31,7 +36,19 @@ trait EntityNormalizerTrait {
       }
       $internal_name = $resource_type->getInternalName($public_field_name);
       $enhancer = $resource_type->getFieldEnhancer($public_field_name, 'publicName');
-      $field_value = $enhancer ? $enhancer->prepareForInput($field_value) : $field_value;
+
+      if (isset($field_storage_definitions[$internal_name])) {
+        $field_storage_definition = $field_storage_definitions[$internal_name];
+        if ($field_storage_definition->getCardinality() === 1) {
+          $field_value = $enhancer ? $enhancer->prepareForInput($field_value) : $field_value;
+        }
+        else {
+          foreach ($field_value as $key => $individual_field_value) {
+            $field_value[$key] = $enhancer ? $enhancer->prepareForInput($individual_field_value) : $individual_field_value;
+          }
+        }
+      }
+
       $data_internal[$internal_name] = $field_value;
     }