diff --git a/src/Bundle/ChillMainBundle/Serializer/Normalizer/UserNormalizer.php b/src/Bundle/ChillMainBundle/Serializer/Normalizer/UserNormalizer.php
index 99e76c5ff..9ab39db5b 100644
--- a/src/Bundle/ChillMainBundle/Serializer/Normalizer/UserNormalizer.php
+++ b/src/Bundle/ChillMainBundle/Serializer/Normalizer/UserNormalizer.php
@@ -18,6 +18,8 @@ use Chill\MainBundle\Entity\Scope;
 use Chill\MainBundle\Entity\User;
 use Chill\MainBundle\Entity\UserJob;
 use Chill\MainBundle\Templating\Entity\UserRender;
+use DateTime;
+use DateTimeImmutable;
 use libphonenumber\PhoneNumber;
 use Symfony\Component\Clock\ClockInterface;
 use Symfony\Component\Serializer\Normalizer\ContextAwareNormalizerInterface;
@@ -45,8 +47,12 @@ class UserNormalizer implements ContextAwareNormalizerInterface, NormalizerAware
     {
     }
 
+    /**
+     * @throws \Symfony\Component\Serializer\Exception\ExceptionInterface
+     */
     public function normalize($object, $format = null, array $context = [])
     {
+        /** @var array{"chill:user:at_date"?: DateTimeImmutable|DateTime} $context */
         /** @var User $object */
         $userJobContext = array_merge(
             $context,
@@ -78,6 +84,9 @@ class UserNormalizer implements ContextAwareNormalizerInterface, NormalizerAware
         }
 
         $at = $context[self::AT_DATE] ?? $this->clock->now();
+        if ($at instanceof DateTime) {
+            $at = DateTimeImmutable::createFromMutable($at);
+        }
 
         $data = [
             'type' => 'user',