diff --git a/core/modules/system/tests/modules/entity_test_update/src/EventSubscriber/EntitySchemaSubscriber.php b/core/modules/system/tests/modules/entity_test_update/src/EventSubscriber/EntitySchemaSubscriber.php
index 31088e9e88..37dac651e2 100644
--- a/core/modules/system/tests/modules/entity_test_update/src/EventSubscriber/EntitySchemaSubscriber.php
+++ b/core/modules/system/tests/modules/entity_test_update/src/EventSubscriber/EntitySchemaSubscriber.php
@@ -8,6 +8,7 @@
 use Drupal\Core\Entity\EntityTypeListenerInterface;
 use Drupal\Core\Field\BaseFieldDefinition;
 use Drupal\Core\State\StateInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
 /**
@@ -55,11 +56,16 @@ public static function getSubscribedEvents() {
    * {@inheritdoc}
    */
   public function onEntityTypeUpdate(EntityTypeInterface $entity_type, EntityTypeInterface $original) {
+    // Only add the new base field when a test needs it.
+    if (!$this->state->get('entity_test_update.install_new_base_field_during_update', FALSE)) {
+      return;
+    }
+
     // Add a new base field when the entity type is updated.
     $definitions = $this->state->get('entity_test_update.additional_base_field_definitions', []);
     $definitions['new_base_field'] = BaseFieldDefinition::create('string')
       ->setName('new_base_field')
-      ->setLabel(t('A new base field'));
+      ->setLabel(new TranslatableMarkup('A new base field'));
     $this->state->set('entity_test_update.additional_base_field_definitions', $definitions);
 
     $this->entityDefinitionUpdateManager->installFieldStorageDefinition('new_base_field', 'entity_test_update', 'entity_test_update', $definitions['new_base_field']);
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php b/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php
index 937a2ab5a4..a525f650eb 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php
@@ -151,13 +151,17 @@ public function testFieldableEntityTypeUpdates($initial_rev, $initial_mul, $new_
       $this->assertEntityData($initial_rev, $initial_mul);
     }
 
+    // Enable the creation of a new base field during a fieldable entity type
+    // update.
+    $this->state->set('entity_test_update.install_new_base_field_during_update', TRUE);
+
     // Simulate a batch run since we are converting the entities one by one.
     $sandbox = [];
     do {
       $this->entityDefinitionUpdateManager->updateFieldableEntityType($updated_entity_type, $updated_field_storage_definitions, $sandbox);
     } while ($sandbox['#finished'] != 1);
 
-    $this->assertEntityTypeSchema($new_rev, $new_mul);
+    $this->assertEntityTypeSchema($new_rev, $new_mul, TRUE);
     $this->assertEntityData($initial_rev, $initial_mul);
 
     $change_list = $this->entityDefinitionUpdateManager->getChangeList();
@@ -427,8 +431,20 @@ protected function assertEntityData($revisionable, $translatable) {
    *   Whether the entity type is revisionable or not.
    * @param bool $translatable
    *   Whether the entity type is translatable or not.
+   * @param bool $new_base_field
+   *   (optional) Whether a new base field was added as part of the update.
+   *   Defaults to FALSE.
    */
-  protected function assertEntityTypeSchema($revisionable, $translatable) {
+  protected function assertEntityTypeSchema($revisionable, $translatable, $new_base_field = FALSE) {
+    // Check whether the 'new_base_field' field has been installed correctly.
+    $field_storage_definition = $this->entityDefinitionUpdateManager->getFieldStorageDefinition('new_base_field', $this->entityTypeId);
+    if ($new_base_field) {
+      $this->assertNotNull($field_storage_definition);
+    }
+    else {
+      $this->assertNull($field_storage_definition);
+    }
+
     if ($revisionable && $translatable) {
       $this->assertRevisionableAndTranslatable();
     }