diff --git a/core/lib/Drupal/Core/Entity/EntityTypeListenerInterface.php b/core/lib/Drupal/Core/Entity/EntityTypeListenerInterface.php
index 0a2b9f3..00c23b7 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeListenerInterface.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeListenerInterface.php
@@ -27,6 +27,11 @@ public function onEntityTypeCreate(EntityTypeInterface $entity_type);
    *   The updated entity type definition.
    * @param \Drupal\Core\Entity\EntityTypeInterface $original
    *   The original entity type definition.
+   *
+   * @return int|NULL
+   *   Returns EntityDefinitionUpdateManager::DEFINITION_UPDATED if the storage
+   *   was updated, EntityDefinitionUpdateManager::DEFINITION_RECREATED if it
+   *   was deleted and recreated or NULL if no action was taken.
    */
   public function onEntityTypeUpdate(EntityTypeInterface $entity_type, EntityTypeInterface $original);
 
diff --git a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
index 5d01610..3d13d7d 100644
--- a/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
+++ b/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php
@@ -313,6 +313,7 @@ public function onEntityTypeUpdate(EntityTypeInterface $entity_type, EntityTypeI
       // Store the updated entity schema.
       $this->saveEntitySchemaData($entity_type, $entity_schema);
     }
+    return EntityDefinitionUpdateManager::DEFINITION_UPDATED;
   }
 
   /**
diff --git a/core/modules/system/src/Tests/Entity/EntityDefinitionUpdateTest.php b/core/modules/system/src/Tests/Entity/EntityDefinitionUpdateTest.php
index 49bcd86..d76af6b 100644
--- a/core/modules/system/src/Tests/Entity/EntityDefinitionUpdateTest.php
+++ b/core/modules/system/src/Tests/Entity/EntityDefinitionUpdateTest.php
@@ -483,8 +483,9 @@ public function testDefinitionEvents() {
   public function testEntityTypeSchemaUpdateAndBaseFieldCreateWithoutData() {
     $this->updateEntityTypeToRevisionable();
     $this->addBaseField();
-    // The base field will be created as part of the entity type update and should not throw an exception when being
-    // created again as part of the field update.
+    // The base field will be created as part of the entity type update and
+    // should not throw an exception when being created again as part of the
+    // field update.
     try {
       $this->entityDefinitionUpdateManager->applyUpdates();
       $this->pass('Successfully updated entity schema and created base field at the same time.');