diff --git a/core/modules/locale/src/LocaleConfigManager.php b/core/modules/locale/src/LocaleConfigManager.php
index e67f3bc..facdaeb 100644
--- a/core/modules/locale/src/LocaleConfigManager.php
+++ b/core/modules/locale/src/LocaleConfigManager.php
@@ -603,10 +603,12 @@ public function updateConfigTranslations(array $names, array $langcodes = []) {
             $count++;
           }
         }
-        elseif (locale_is_translatable($langcode)) {
+        elseif (locale_is_translatable($langcode) && $name != 'system.site') {
           // If the language code is the active storage language, we should
           // update. If it is English, we should only update if English is also
-          // translatable.
+          // translatable. The system.site configuration is special because it
+          // is written during installation using the langcode at installation
+          // time.
           $active = NestedArray::mergeDeepArray([$active, $processed], TRUE);
           $this->saveTranslationActive($name, $active);
           $count++;