core/modules/rest/src/Annotation/RestResource.php | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/core/modules/rest/src/Annotation/RestResource.php b/core/modules/rest/src/Annotation/RestResource.php
index 28293b6..b0310b9 100644
--- a/core/modules/rest/src/Annotation/RestResource.php
+++ b/core/modules/rest/src/Annotation/RestResource.php
@@ -43,4 +43,13 @@ class RestResource extends Plugin {
    */
   public $label;
 
+  /**
+   * Optional; only necessary for writable REST resources.
+   *
+   * @see \Symfony\Component\Serializer\SerializerInterface's "type" parameter.
+   *
+   * @var string
+   */
+  public $serialization_class;
+
 }