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
@@ -275,7 +275,7 @@
     }
   }
 
-  /*
+  /**
    * Form submission handler for the incremental overview form.
    *
    * @param array $form
@@ -884,7 +884,7 @@
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form.
    */
-  protected function setupMigrations($database, FormStateInterface $form_state) {
+  protected function setupMigrations(array $database, FormStateInterface $form_state) {
     $connection = $this->getConnection($database);
     $version = $this->getLegacyDrupalVersion($connection);
     $this->createDatabaseStateSettings($database, $version);