src/ResourceType/ResourceTypeRepository.php | 6 ++++++
 tests/src/Functional/ResourceTestBase.php   | 1 +
 2 files changed, 7 insertions(+)

diff --git a/src/ResourceType/ResourceTypeRepository.php b/src/ResourceType/ResourceTypeRepository.php
index 34b20af..be87c1c 100644
--- a/src/ResourceType/ResourceTypeRepository.php
+++ b/src/ResourceType/ResourceTypeRepository.php
@@ -72,6 +72,12 @@ class ResourceTypeRepository implements ResourceTypeRepositoryInterface {
     $this->entityFieldManager = $entity_field_manager;
   }
 
+  // @todo implement \Drupal\Core\Plugin\CachedDiscoveryClearerInterface?
+  // @todo implement \Drupal\Component\Plugin\Discovery\DiscoveryInterface?
+  public function clearCachedDefinitions() {
+    $this->all = [];
+  }
+
   /**
    * {@inheritdoc}
    */
diff --git a/tests/src/Functional/ResourceTestBase.php b/tests/src/Functional/ResourceTestBase.php
index b25f7c0..ce86a57 100644
--- a/tests/src/Functional/ResourceTestBase.php
+++ b/tests/src/Functional/ResourceTestBase.php
@@ -108,6 +108,7 @@ abstract class ResourceTestBase extends BrowserTestBase {
     $this->entityStorage = $this->container->get('entity_type.manager')
       ->getStorage(static::$entityTypeId);
     $this->entity = $this->createEntity();
+    \Drupal::service('jsonapi.resource_type.repository')->clearCachedDefinitions();
     \Drupal::service('router.builder')->rebuild();
 
     /*