diff -u b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
--- b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -66,7 +66,7 @@
       'source_module' => 'block',
       'destination_module' => 'block',
     ],
-    'd6_i18n_block' => [
+    'd6_block_translation' => [
       'source_module' => 'i18n',
       'destination_module' => 'content_translation',
     ],
@@ -86,7 +86,7 @@
       'source_module' => 'block',
       'destination_module' => 'block_content',
     ],
-    'd6_i18n_custom_block' => [
+    'd6_custom_block_translation' => [
       'source_module' => 'i18n',
       'destination_module' => 'content_translation',
     ],