diff --git a/core/modules/config_translation/src/FormElement/FormElementBase.php b/core/modules/config_translation/src/FormElement/FormElementBase.php
index e13cc31..ceca9c3 100644
--- a/core/modules/config_translation/src/FormElement/FormElementBase.php
+++ b/core/modules/config_translation/src/FormElement/FormElementBase.php
@@ -12,6 +12,7 @@
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\Core\TypedData\TypedDataInterface;
 use Drupal\language\Config\LanguageConfigOverride;
+use Drupal\locale\SourceString;
 
 /**
  * Provides a common base class for form elements.
@@ -66,11 +67,32 @@ public function getTranslationBuild(LanguageInterface $source_language, Language
     // configuration values in ConfigTranslationFormBase::setConfig().
     // Therefore we make the 'source' and 'translation' keys the top-level
     // keys in $form_state['values'].
-    $build['source'] = $this->getSourceElement($source_language, $source_config);
-    $build['translation'] = $this->getTranslationElement($translation_language, $source_config, $translation_config);
 
-    $build['source']['#parents'] = array_merge(array('source'), $parents);
-    $build['translation']['#parents'] = array_merge(array('translation'), $parents);
+    // Cast into source string, will do for our purposes.
+    $source = new SourceString(array('source' => $translation_config));
+    // Split source to work with plural values.
+    $source_array = $source->getPlurals();
+    if (count($source_array) == 1) {
+      $build['source'] = $this->getSourceElement($source_language, $source_config);
+      $build['translation'] = $this->getTranslationElement($translation_language, $source_config, $translation_config);
+
+      $build['source']['#parents'] = array_merge(array('source'), $parents);
+      $build['translation']['#parents'] = array_merge(array('translation'), $parents);
+    }
+    else {
+      $build['source'][0] = $this->getSourceElement($source_language, $source_array[0]);
+      $build['translation'][0] = $this->getTranslationElement($translation_language, $source_config, $source_array[0]);
+
+      $build['source'][0]['#parents'] = array_merge(array('source'), $parents);
+      $build['translation'][0]['#parents'] = array_merge(array('translation'), $parents);
+
+      $build['source'][1] = $this->getSourceElement($source_language, $source_array[1]);
+      $build['translation'][1] = $this->getTranslationElement($translation_language, $source_config, $source_array[1]);
+
+      $build['source'][1]['#parents'] = array_merge(array('source'), $parents);
+      $build['translation'][1]['#parents'] = array_merge(array('translation'), $parents);
+    }
+
     return $build;
   }
 
@@ -83,7 +105,7 @@ public function getTranslationBuild(LanguageInterface $source_language, Language
    * translator.
    *
    * @param \Drupal\Core\Language\LanguageInterface $source_language
-   *   Thee source language of the configuration object.
+   *   The source language of the configuration object.
    * @param mixed $source_config
    *   The configuration value of the element in the source language.
    *