diff --git a/core/modules/jsonapi/src/Controller/EntityResource.php b/core/modules/jsonapi/src/Controller/EntityResource.php
index 5c86a47d70..8a7cd7bd0c 100644
--- a/core/modules/jsonapi/src/Controller/EntityResource.php
+++ b/core/modules/jsonapi/src/Controller/EntityResource.php
@@ -655,7 +655,7 @@ public function replaceRelationshipData(ResourceType $resource_type, EntityInter
     $this->validate($entity);
     $entity->save();
     $requires_response = static::relationshipResponseRequiresBody($resource_identifiers, ResourceIdentifier::toResourceIdentifiersWithArityRequired($field_list));
-    return $this->getRelationship($resource_type, $entity, $related, $request, $requires_response ? 200 : 204);
+    return $this->getRelationship($resource_type, $entity, $resource_type->getPublicName($related), $request, $requires_response ? 200 : 204);
   }
 
   /**
diff --git a/core/modules/jsonapi/src/JsonApiResource/ResourceObject.php b/core/modules/jsonapi/src/JsonApiResource/ResourceObject.php
index 7ed9042dd4..2e9c38d1f4 100644
--- a/core/modules/jsonapi/src/JsonApiResource/ResourceObject.php
+++ b/core/modules/jsonapi/src/JsonApiResource/ResourceObject.php
@@ -303,6 +303,10 @@ protected static function extractContentEntityFields(ResourceType $resource_type
       $is_relationship = in_array($public_field_name, $relationship_field_names, TRUE);
       if ($field_access_result->isAllowed()) {
         assert(!$is_relationship || $field_value instanceof EntityReferenceFieldItemListInterface);
+        // Access cacheability needs to be specially captured for the "allowed"
+        // case. In the other case, cacheability is captured by the
+        // EntityAccessDeniedException.
+        $entity->addCacheableDependency($field_access_result);
         $output[$public_field_name] = $is_relationship ? Relationship::createFromEntityReferenceField($resource_type, $field_value) : $field_value;
       }
       else {
diff --git a/core/modules/jsonapi/src/Normalizer/RelationshipNormalizer.php b/core/modules/jsonapi/src/Normalizer/RelationshipNormalizer.php
index 1ce4d0336e..53354af0b6 100644
--- a/core/modules/jsonapi/src/Normalizer/RelationshipNormalizer.php
+++ b/core/modules/jsonapi/src/Normalizer/RelationshipNormalizer.php
@@ -24,7 +24,7 @@ public function normalize($object, $format = NULL, array $context = []) {
     assert($object instanceof Relationship);
     return CacheableNormalization::aggregate([
       'data' => $this->serializer->normalize($object->getData(), $format, $context),
-      'links' => $this->serializer->normalize($object->getLinks(), $format, $context),
+      'links' => $this->serializer->normalize($object->getLinks(), $format, $context)->omitIfEmpty(),
       'meta' => CacheableNormalization::permanent($object->getMeta())->omitIfEmpty(),
     ]);
   }