diff --git a/core/modules/locale/src/Tests/LocaleTranslatedSchemaDefinitionTest.php b/core/modules/locale/src/Tests/LocaleTranslatedSchemaDefinitionTest.php
index ba7f2c2..4f933ce 100644
--- a/core/modules/locale/src/Tests/LocaleTranslatedSchemaDefinitionTest.php
+++ b/core/modules/locale/src/Tests/LocaleTranslatedSchemaDefinitionTest.php
@@ -31,6 +31,8 @@ protected function setUp() {
     parent::setUp();
     ConfigurableLanguage::createFromLangcode('fr')->save();
     $this->config('system.site')->set('langcode', 'fr')->save();
+    // Clear all caches so that the base field definition, its cache in
+    // the entity manager, the t() cache, etc. are all cleared.
     drupal_flush_all_caches();
   }