diff --git a/core/lib/Drupal/Core/Entity/EntityTypeListener.php b/core/lib/Drupal/Core/Entity/EntityTypeListener.php
index 8e256f41b2..a8c90c4861 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeListener.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeListener.php
@@ -128,7 +128,7 @@ public function onFieldableEntityTypeUpdate(EntityTypeInterface $entity_type, En
       $storage->onFieldableEntityTypeUpdate($entity_type, $original, $field_storage_definitions, $original_field_storage_definitions, $sandbox);
     }
 
-    if ($sandbox === NULL || (isset($sandbox['#finished']) && $sandbox['#finished'] === 1)) {
+    if ($sandbox === NULL || (isset($sandbox['#finished']) && $sandbox['#finished'] == 1)) {
       $this->eventDispatcher->dispatch(EntityTypeEvents::UPDATE, new EntityTypeEvent($entity_type, $original));
 
       $this->entityLastInstalledSchemaRepository->setLastInstalledDefinition($entity_type);
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
index 6387d70427..dba62bdc74 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
@@ -450,10 +450,7 @@ protected function preUpdateEntityTypeSchema(EntityTypeInterface $entity_type, E
     // Filter out tables which are not part of the table mapping.
     $schema = array_intersect_key($schema, $temporary_table_names);
     foreach ($schema as $table_name => $table_schema) {
-      $temp_table_name = $temporary_table_names[$table_name];
-      if (!$schema_handler->tableExists($temp_table_name)) {
-        $schema_handler->createTable($temp_table_name, $table_schema);
-      }
+      $schema_handler->createTable($temporary_table_names[$table_name], $table_schema);
     }
 
     // Create dedicated field tables.
@@ -464,10 +461,7 @@ protected function preUpdateEntityTypeSchema(EntityTypeInterface $entity_type, E
         // Filter out tables which are not part of the table mapping.
         $schema = array_intersect_key($schema, $temporary_table_names);
         foreach ($schema as $table_name => $table_schema) {
-          $temp_table_name = $temporary_table_names[$table_name];
-          if (!$schema_handler->tableExists($temp_table_name)) {
-            $schema_handler->createTable($temp_table_name, $table_schema);
-          }
+          $schema_handler->createTable($temporary_table_names[$table_name], $table_schema);
         }
       }
     }
@@ -523,8 +517,8 @@ protected function postUpdateEntityTypeSchema(EntityTypeInterface $entity_type,
           $this->createDedicatedTableSchema($field_storage_definition, TRUE);
         }
         elseif ($new_table_mapping->allowsSharedTableStorage($field_storage_definition)) {
-          // The shared tables are already fully created, but we need to save the
-          // per-field schema definitions for later use.
+          // The shared tables are already fully created, but we need to save
+          // the per-field schema definitions for later use.
           $this->createSharedTableSchema($field_storage_definition, TRUE);
         }
       }
@@ -547,6 +541,8 @@ protected function postUpdateEntityTypeSchema(EntityTypeInterface $entity_type,
 
     // At this point the update process either finished successfully or any
     // error has been thrown already, so we can drop the backup entity tables.
+    // @todo Decide whether we should keep these tables around.
+    //   @see https://www.drupal.org/project/drupal/issues/3024728
     foreach ($backup_table_names as $original_table_name => $backup_table_name) {
       $this->database->schema()->dropTable($backup_table_name);
     }
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlFieldableEntityTypeListenerTrait.php b/core/lib/Drupal/Core/Entity/Sql/SqlFieldableEntityTypeListenerTrait.php
index 0dd808e9c2..bec6f5602f 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlFieldableEntityTypeListenerTrait.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlFieldableEntityTypeListenerTrait.php
@@ -24,8 +24,10 @@ public function onFieldableEntityTypeUpdate(EntityTypeInterface $entity_type, En
     $has_data = $original_storage->hasData();
 
     // We cannot support updating the schema of an entity type from revisionable
-    // to non-revisionable or translatable to non-translatable because that
-    // implies data loss.
+    // to non-revisionable or translatable to non-translatable because that can
+    // lead to unintended data loss.
+    // @todo Add support for these conversions in case there is no data loss.
+    //   @see https://www.drupal.org/project/drupal/issues/3024727
     $convert_rev_to_non_rev = $original->isRevisionable() && !$entity_type->isRevisionable();
     $convert_mul_to_non_mul = $original->isTranslatable() && !$entity_type->isTranslatable();
     if ($has_data && ($convert_rev_to_non_rev || $convert_mul_to_non_mul)) {
@@ -75,7 +77,7 @@ public function onFieldableEntityTypeUpdate(EntityTypeInterface $entity_type, En
     // If the data copying has finished successfully, allow the storage schema
     // to do any required cleanup tasks. For example, this process should take
     // care of transforming the temporary storage into the current storage.
-    if ($sandbox['#finished'] === 1) {
+    if ($sandbox['#finished'] == 1) {
       $this->postUpdateEntityTypeSchema($entity_type, $original, $field_storage_definitions, $original_field_storage_definitions, $sandbox);
     }
   }
diff --git a/core/modules/system/tests/src/Functional/Entity/Traits/EntityDefinitionTestTrait.php b/core/modules/system/tests/src/Functional/Entity/Traits/EntityDefinitionTestTrait.php
index 2633beb929..8cf74829ea 100644
--- a/core/modules/system/tests/src/Functional/Entity/Traits/EntityDefinitionTestTrait.php
+++ b/core/modules/system/tests/src/Functional/Entity/Traits/EntityDefinitionTestTrait.php
@@ -302,7 +302,7 @@ protected function deleteEntityType() {
    *
    * @param bool $revisionable
    *   (optional) Whether the entity type should be revisionable or not.
-   *   Defaults toFALSE.
+   *   Defaults to FALSE.
    * @param bool $translatable
    *   (optional) Whether the entity type should be translatable or not.
    *   Defaults to FALSE.
@@ -353,7 +353,7 @@ protected function getUpdatedEntityTypeDefinition($revisionable = FALSE, $transl
    *
    * @param bool $revisionable
    *   (optional) Whether the entity type should be revisionable or not.
-   *   Defaults toFALSE.
+   *   Defaults to FALSE.
    * @param bool $translatable
    *   (optional) Whether the entity type should be translatable or not.
    *   Defaults to FALSE.
diff --git a/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php b/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php
index 3c764d6095..e2f041804a 100644
--- a/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Entity/FieldableEntityDefinitionUpdateTest.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Entity\EntityStorageException;
 use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\Site\Settings;
 use Drupal\language\Entity\ConfigurableLanguage;
 use Drupal\Tests\system\Functional\Entity\Traits\EntityDefinitionTestTrait;
 
@@ -86,6 +87,11 @@ protected function setUp() {
 
     // Enable an additional language.
     ConfigurableLanguage::createFromLangcode('ro')->save();
+
+    // Force the update function to convert one entity at a time.
+    $settings = Settings::getAll();
+    $settings['entity_update_batch_size'] = 1;
+    new Settings($settings);
   }
 
   /**
@@ -115,8 +121,12 @@ public function testFieldableEntityTypeUpdates($initial_rev, $initial_mul, $new_
       $this->setExpectedException(EntityStorageException::class, 'Converting an entity type from revisionable to non-revisionable or from translatable to non-translatable is not supported.');
     }
 
+    // Simulate a batch run since we are converting the entities one by one.
     $sandbox = [];
-    $this->entityDefinitionUpdateManager->updateFieldableEntityType($updated_entity_type, $updated_field_storage_definitions, $sandbox);
+    do {
+      $this->entityDefinitionUpdateManager->updateFieldableEntityType($updated_entity_type, $updated_field_storage_definitions, $sandbox);
+    } while ($sandbox['#finished'] != 1);
+
     $this->assertEntityTypeSchema($new_rev, $new_mul);
     $this->assertEntityData($initial_rev, $initial_mul);
   }