diff --git a/core/modules/locale/src/LocaleTranslation.php b/core/modules/locale/src/LocaleTranslation.php
index e9b693894e5..a9ccc93626f 100644
--- a/core/modules/locale/src/LocaleTranslation.php
+++ b/core/modules/locale/src/LocaleTranslation.php
@@ -119,6 +119,11 @@ class LocaleTranslation implements TranslatorInterface, DestructableInterface {
       $this->translations[$langcode][$context] = new LocaleLookup($langcode, $context, $this->storage, $this->cache, $this->lock, $this->configFactory, $this->languageManager, $this->requestStack);
     }
     $translation = $this->translations[$langcode][$context]->get($string);
+    // If the translation is TRUE, no translation exists, but that string needs
+    // to be stored in the persistent cache for performance reasons (so for
+    // example, we don't have hundreds of queries to locale tables on each
+    // request). That cache is persisted when the request ends, and the lookup
+    // service is destroyed.
     return $translation === TRUE ? FALSE : $translation;
   }