diff --git a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
index 2d60c46..99c2af7 100644
--- a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -82,6 +82,10 @@ class MigrateUpgradeForm extends ConfirmFormBase {
       'source_module' => 'block',
       'destination_module' => 'block_content',
     ],
+    'd6_i18n_custom_block' => [
+      'source_module' => 'translation',
+      'destination_module' => 'content_translation',
+    ],
     'd7_custom_block' => [
       'source_module' => 'block',
       'destination_module' => 'block_content',