diff --git a/core/modules/locale/src/LocaleConfigManager.php b/core/modules/locale/src/LocaleConfigManager.php
index 920ef54..647df06 100644
--- a/core/modules/locale/src/LocaleConfigManager.php
+++ b/core/modules/locale/src/LocaleConfigManager.php
@@ -166,6 +166,8 @@ protected function getTranslatableData(TypedDataInterface $element) {
    *
    * @param string $name
    *   The configuration name.
+   * @param array $active
+   *   The active configuration data.
    * @param array $translatable
    *   The translatable array structure, see this::getTranslatableData().
    * @param string $langcode
@@ -176,10 +178,13 @@ protected function getTranslatableData(TypedDataInterface $element) {
    *   different from source strings or in case of untranslatable English, the
    *   source strings themselves.
    */
-  protected function processTranslatableData($name, array $translatable, $langcode) {
+  protected function processTranslatableData($name, array $active, array $translatable, $langcode) {
     $translated = array();
     foreach ($translatable as $key => $item) {
-      if (is_array($item) && $value = $this->processTranslatableData($name, $item, $langcode)) {
+      if (!isset($active[$key])) {
+        continue;
+      }
+      if (is_array($item) && $value = $this->processTranslatableData($name, $active[$key], $item, $langcode)) {
         $translated[$key] = $value;
       }
       else {
@@ -196,36 +201,6 @@ protected function processTranslatableData($name, array $translatable, $langcode
   }
 
   /**
-   * Compares default configuration with updated data.
-   *
-   * @param array $default
-   *   Default configuration data.
-   * @param array|false $updated
-   *   Current configuration data, or FALSE if no configuration data existed.
-   *
-   * @return array
-   *   The elements of default configuration that haven't changed.
-   */
-  protected function compareConfigData(array $default, $updated) {
-    // Speed up comparison, specially for install operations.
-    if ($default === $updated) {
-      return $default;
-    }
-    $result = array();
-    foreach ($default as $key => $value) {
-      if (isset($updated[$key])) {
-        if (is_array($value)) {
-          $result[$key] = $this->compareConfigData($value, $updated[$key]);
-        }
-        elseif ($value === $updated[$key]) {
-          $result[$key] = $value;
-        }
-      }
-    }
-    return $result;
-  }
-
-  /**
    * Saves translated configuration override.
    *
    * @param string $name
@@ -437,12 +412,16 @@ public function hasTranslation($name, $langcode) {
    *
    * @param $name
    *   The configuration name.
-   * @return string
-   *   Language code of the original shipped configuration.
+   *
+   * @return null|string
+   *   Language code of the original shipped configuration. NULL if no such
+   *   default configuration.
    */
   public function defaultConfigLangcode($name) {
     $shipped = $this->installStorageRead($name);
-    return $shipped['langcode'] ?: 'en';
+    if (!empty($shipped)) {
+      return $shipped['langcode'] ?: 'en';
+    }
   }
 
   /**
@@ -450,12 +429,16 @@ public function defaultConfigLangcode($name) {
    *
    * @param $name
    *   The configuration name.
-   * @return string
-   *   Language code of the current active configuration.
+   *
+   * @return null|string
+   *   Language code of the current active configuration. NULL if no such active
+   *   configuration.
    */
   public function activeConfigLangcode($name) {
     $active = $this->configStorage->read($name);
-    return $active['langcode'] ?: 'en';
+    if (!empty($active)) {
+      return $active['langcode'] ?: 'en';
+    }
   }
 
   /**
@@ -451,7 +451,7 @@ public function activeConfigLangcode($name) {
    *   TRUE if interface translation is supported.
    */
   public function isSupported($name) {
-    return $this->defaultConfigLangcode($name) == 'en';
+    return $this->defaultConfigLangcode($name) == 'en' && !is_null($this->activeConfigLangcode($name));
   }

   /**
@@ -463,6 +446,7 @@ public function activeConfigLangcode($name) {
    *
    * @param $name
    *   The configuration name.
+   *
    * @return bool
    *   TRUE if interface translation is supported.
    */
@@ -475,11 +459,15 @@ public function isSupported($name) {
    *
    * @param $name
    *   The configuration name.
+   *
    * @return bool
-   *   TRUE if interface translation is supported.
+   *   TRUE if the configuration both exists as default and active configuration
+   *   and their language codes don't match.
    */
   public function isTranslatedConfig($name) {
-    return $this->defaultConfigLangcode($name) != $this->activeConfigLangcode($name);
+    $default_langcode = $this->defaultConfigLangcode($name);
+    $active_langcode = $this->activeConfigLangcode($name);
+    return !is_null($default_langcode) && !is_null($active_langcode) && $default_langcode != $active_langcode;
   }
 
   /**
@@ -511,14 +499,20 @@ public function updateConfigTranslations(array $names, array $langcodes = array(
     $langcodes = $langcodes ? $langcodes : array_keys($this->languageManager->getLanguages());
     $count = 0;
     foreach ($names as $name) {
+      // Only deal with configuration which was shipped.
       if (!$this->isSupported($name)) {
         continue;
       }
 
       $translatable = $this->getTranslatableDefaultConfig($name);
+      $active_langcode = $this->activeConfigLangcode($name);
+      $active = $this->configStorage->read($name);
+
       foreach ($langcodes as $langcode) {
-        $processed = $this->processTranslatableData($name, $translatable, $langcode);
-        if ($langcode != 'en' || !$this->isTranslatedConfig($name)) {
+        $processed = $this->processTranslatableData($name, $active, $translatable, $langcode);
+        if ($langcode != $active_langcode) {
+          // If the language code is not the same as the active storage
+          // language, we should update a configuration override.
           if ($processed) {
             // Update translation data in configuration override.
             $this->saveTranslationOverride($name, $langcode, $processed);
@@ -530,7 +524,9 @@ public function updateConfigTranslations(array $names, array $langcodes = array(
           }
         }
         elseif ($langcode != 'en' || locale_translate_english()) {
-          $active = $this->configStorage->read($name);
+          // 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.
           $active = $this->mergeToActiveConfig($active, $processed);
           $this->saveTranslationActive($name, $active);
         }