diff --git a/tests/src/Kernel/ExternalLibraryKernelTestBase.php b/tests/src/Kernel/ExternalLibraryKernelTestBase.php
index 18754144b022bbb83d8856730ec0e4956f49068c..938214e6b7f513c7b53e51bd6b6b06d1e7d3e487 100644
--- a/tests/src/Kernel/ExternalLibraryKernelTestBase.php
+++ b/tests/src/Kernel/ExternalLibraryKernelTestBase.php
@@ -16,7 +16,7 @@ use Drupal\Core\Site\Settings;
 /**
  * Provides an improved version of the core kernel test base class.
  */
-class ExternalLibraryKernelTestBase extends CoreKernelTestBase {
+abstract class ExternalLibraryKernelTestBase extends CoreKernelTestBase {
 
   /**
    * {@inheritdoc}