src/Controller/EntityResource.php                  | 2 +-
 tests/src/Functional/JsonApiFunctionalTest.php     | 4 ++++
 tests/src/Functional/JsonApiFunctionalTestBase.php | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/Controller/EntityResource.php b/src/Controller/EntityResource.php
index 54d2622..8cdd274 100644
--- a/src/Controller/EntityResource.php
+++ b/src/Controller/EntityResource.php
@@ -396,7 +396,7 @@ class EntityResource {
       ->getDataDefinition()
       ->getFieldStorageDefinition()
       ->isMultiple();
-    if (!$is_multiple) {
+    if (!$is_multiple && $field_list->entity) {
       $response = $this->getIndividual($field_list->entity, $request);
       // Add cacheable metadata for host entity to individual response.
       $response->addCacheableDependency($cacheable_metadata);
diff --git a/tests/src/Functional/JsonApiFunctionalTest.php b/tests/src/Functional/JsonApiFunctionalTest.php
index a2751f0..b2cffd0 100644
--- a/tests/src/Functional/JsonApiFunctionalTest.php
+++ b/tests/src/Functional/JsonApiFunctionalTest.php
@@ -91,6 +91,10 @@ class JsonApiFunctionalTest extends JsonApiFunctionalTestBase {
     $this->assertArrayHasKey('type', $single_output['data'][0]);
     $this->assertArrayNotHasKey('attributes', $single_output['data'][0]);
     $this->assertArrayHasKey('related', $single_output['links']);
+    // 8b. Single related item, empty.
+    $single_output = Json::decode($this->drupalGet('/jsonapi/node/article/' . $uuid . '/field_heroless'));
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSame([], $single_output['data']);
     // 9. Related tags with includes.
     $single_output = Json::decode($this->drupalGet('/jsonapi/node/article/' . $uuid . '/field_tags', [
       'query' => ['include' => 'vid'],
diff --git a/tests/src/Functional/JsonApiFunctionalTestBase.php b/tests/src/Functional/JsonApiFunctionalTestBase.php
index abcfb02..f683a22 100644
--- a/tests/src/Functional/JsonApiFunctionalTestBase.php
+++ b/tests/src/Functional/JsonApiFunctionalTestBase.php
@@ -122,6 +122,7 @@ abstract class JsonApiFunctionalTestBase extends BrowserTestBase {
         FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED
       );
       $this->createImageField('field_image', 'article');
+      $this->createImageField('field_heroless', 'article');
     }
 
     FieldStorageConfig::create([