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
@@ -757,8 +757,14 @@
     // Retrieve the database driver from state.
     // @todo harden this.
     $database_state_key = \Drupal::state()->get('migrate.fallback_state_key', '');
-    $database = \Drupal::state()->get($database_state_key, [])['database'];
-    $this->setUpSourceAndMigrations($form_state, $database);
+    if ($database_state_key) {
+      $database = \Drupal::state()->get($database_state_key, [])['database'];
+      $this->setUpSourceAndMigrations($form_state, $database);
+    }
+    else {
+      $form_state->setValue('step', 'credentials');
+      $form_state->setRebuild();
+    }
   }
 
   /**