diff --git a/core/modules/content_translation/migrations/d6_custom_block_translation.yml b/core/modules/content_translation/migrations/d6_custom_block_translation.yml
index bbe7833a67..1b4f9b87c4 100644
--- a/core/modules/content_translation/migrations/d6_custom_block_translation.yml
+++ b/core/modules/content_translation/migrations/d6_custom_block_translation.yml
@@ -4,27 +4,35 @@ migration_tags:
   - Drupal 6
 source:
   plugin: d6_box_translation
-  constants:
-    type: basic
 process:
   id:
-    plugin: migration
+    plugin: migration_lookup
     migration: d6_custom_block
     source:
       - bid
   langcode: language
   info:
-    plugin: i18n_translation
-    source:
-      - title_untranslated
-      - title_translated
+    -
+      plugin: callback
+      source:
+        - title_translated
+        - title_untranslated
+      callable: array_filter
+    -
+      plugin: callback
+      callable: reset
   'body/value':
-    plugin: i18n_translation
-    source:
-      - body_untranslated
-      - body_translated
+    -
+      plugin: callback
+      source:
+        - body_translated
+        - body_untranslated
+      callable: array_filter
+    -
+      plugin: callback
+      callable: reset
   'body/format':
-    plugin: migration
+    plugin: migration_lookup
     migration: d6_filter_format
     source: format
 destination:
diff --git a/core/modules/content_translation/src/Plugin/migrate/process/d6/i18nTranslation.php b/core/modules/content_translation/src/Plugin/migrate/process/d6/i18nTranslation.php
deleted file mode 100644
index 08a3e0546e..0000000000
--- a/core/modules/content_translation/src/Plugin/migrate/process/d6/i18nTranslation.php
+++ /dev/null
@@ -1,51 +0,0 @@
-<?php
-
-namespace Drupal\content_translation\Plugin\migrate\process\d6;
-
-use Drupal\migrate\MigrateException;
-use Drupal\migrate\MigrateExecutableInterface;
-use Drupal\migrate\ProcessPluginBase;
-use Drupal\migrate\Row;
-
-/**
- * Processes an i18n translation.
- *
- * The i18n_translation plugin will return the translated value, if provided,
- * otherwise it will return the untranslated value.
- *
- * Available configuration keys:
- * - source: An array of two values, the first is the untranslated value and the
- * second is the translated value.
- *
- * Example:
- * @code
- * process:
- *   bar:
- *     plugin: i18n_translation
- *     source:
- *       - foo
- *       - oof
- * @endcode
- *
- * In this example, the string 'oof' is returned.
- *
- * @throws \Drupal\migrate\MigrateException
- *
- * @MigrateProcessPlugin(
- *   id = "i18n_translation"
- * )
- */
-class i18nTranslation extends ProcessPluginBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
-    if (!is_array($value) || count($value) !== 2) {
-      throw new MigrateException('You need to specify both the translated and untranslated values on the i18n_translation plugin.');
-    }
-    list($untranslated, $translated) = $value;
-    return $translated ?: $untranslated;
-  }
-
-}
diff --git a/core/modules/content_translation/src/Plugin/migrate/source/d6/BoxTranslation.php b/core/modules/content_translation/src/Plugin/migrate/source/d6/BoxTranslation.php
index a82c2a4bc9..b0dc47f3f6 100644
--- a/core/modules/content_translation/src/Plugin/migrate/source/d6/BoxTranslation.php
+++ b/core/modules/content_translation/src/Plugin/migrate/source/d6/BoxTranslation.php
@@ -15,17 +15,16 @@
  * )
  */
 class BoxTranslation extends DrupalSqlBase {
-
   /**
    * {@inheritdoc}
    */
   public function query() {
-    if (($this->getDatabase()->schema()->tableExists('i18n_strings')) &&
-      $this->getDatabase()->schema()->tableExists('locales_target')) {
+    $schema = $this->getDatabase()->schema();
+    if ($schema->tableExists('i18n_strings') && $schema->tableExists('locales_target')) {
       // Build a query based on 18n_strings table where each row has the
       // translation for only one property, either title or description. The
-      // method prepareRow() is then used to obtain the translation for the other
-      // property.
+      // method prepareRow() is then used to obtain the translation for the
+      // other property.
       $query = $this->select('boxes', 'b')
         ->fields('b', ['bid', 'body', 'info', 'format'])
         ->fields('i18n', ['lid', 'property'])
@@ -62,16 +61,16 @@ public function prepareRow(Row $row) {
     $row->setSourceProperty($property . '_translated', $row->getSourceProperty('translation'));
 
     // Get the translation for the property not already in the row.
-    $property2 = ($property == 'title') ? 'body' : 'title';
+    $translation = ($property == 'title') ? 'body' : 'title';
     $query = $this->select('i18n_strings', 'i18n')
       ->fields('i18n', ['lid'])
-      ->condition('i18n.property', $property2)
+      ->condition('i18n.property', $translation)
       ->condition('i18n.objectid', $bid);
     $query->leftJoin('locales_target', 'lt', 'i18n.lid = lt.lid');
     $query->condition('lt.language', $language)
       ->addField('lt', 'translation');
     $results = $query->execute()->fetchAssoc();
-    $row->setSourceProperty($property2 . '_translated', $results['translation']);
+    $row->setSourceProperty($translation . '_translated', $results['translation']);
   }
 
   /**