diff --git a/core/modules/file/src/Plugin/migrate/source/d7/File.php b/core/modules/file/src/Plugin/migrate/source/d7/File.php
index 0c1b00d..93d92e4 100644
--- a/core/modules/file/src/Plugin/migrate/source/d7/File.php
+++ b/core/modules/file/src/Plugin/migrate/source/d7/File.php
@@ -89,11 +89,9 @@ public function prepareRow(Row $row) {
     // At this point, $path could be an absolute path or a relative path,
     // depending on how the scheme's variable was set. So we need to shear out
     // the source_base_path in order to make them all relative.
-    // @todo Don't depend on destination configuration.
-    // @see https://www.drupal.org/node/2577871
-
-    // @TODO, figure out why this is done here and not the destination.
-    // $path = str_replace($this->migration->get('destination')['source_base_path'], NULL, $path);
+    // @todo Don't depend on destination configuration and figure out if this is
+    // even needed at all? https://www.drupal.org/node/2577871
+    $path = str_replace($this->migration->get('destination')['source_base_path'], NULL, $path);
     $row->setSourceProperty('filepath', $path);
     return parent::prepareRow($row);
   }
diff --git a/core/modules/migrate_drupal/src/MigrationCreationTrait.php b/core/modules/migrate_drupal/src/MigrationCreationTrait.php
index 8cd2373..8287ff9 100644
--- a/core/modules/migrate_drupal/src/MigrationCreationTrait.php
+++ b/core/modules/migrate_drupal/src/MigrationCreationTrait.php
@@ -96,37 +96,20 @@ protected function getSourceDatabaseConnection(array $database) {
    *   The state key.
    * @param int $drupal_version
    *   The version of Drupal we're getting the migrations for.
-   * @param string $source_base_path
-   *   (optional) Address of the source Drupal site (e.g., http://example.com/).
    *
    * @return \Drupal\migrate\Entity\MigrationInterface[]
    *   The migrations for import.
    */
-  protected function getMigrations($database_state_key, $drupal_version, $source_base_path = '') {
+  protected function getMigrations($database_state_key, $drupal_version) {
     $version_tag = 'Drupal ' . $drupal_version;
     $plugin_manager = \Drupal::service('plugin.manager.migration');
     /** @var \Drupal\migrate\Plugin\Migration[] $all_migrations */
     $all_migrations = $plugin_manager->createInstancesByTag($version_tag);
     $migrations = [];
     foreach ($all_migrations as $migration) {
-      // @TODO :/
-//      // Set the state key into the source.
-//      $source = $migration->get('source');
-//      $source['database_state_key'] = $database_state_key;
-//      $migration->set('source', $source);
-//
-//      // Setup the destination for the file destination.
-//      $destination = $migration->get('destination');
-//      if ($destination['plugin'] == 'entity:file') {
-//        if ($source_base_path) {
-//          // Make sure we have a single trailing slash.
-//          $source_base_path = rtrim($source_base_path, '/') . '/';
-//          $destination['source_base_path'] = $source_base_path;
-//          $migration->set('destination', $destination);
-//        }
-//      }
-
       try {
+        // @TODO, we should be able to validate the entire migration at this
+        // point. https://drupal.org/node/2625696
         $source_plugin = $migration->getSourcePlugin();
         if ($source_plugin instanceof RequirementsInterface) {
           $source_plugin->checkRequirements();
diff --git a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
index 938f3c9..7476d18 100644
--- a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -948,7 +948,7 @@ public function validateCredentialForm(array &$form, FormStateInterface $form_st
 
     try {
       $version = $this->getLegacyDrupalVersion($this->getSourceDatabaseConnection($database));
-      $migrations = $this->getMigrations('migrate_drupal_' . $version, $version, $form_state->getValue('source_base_path'));
+      $migrations = $this->getMigrations('migrate_drupal_' . $version, $version);
 
       // Get the system data from source database.
       $system_data = $this->getSystemData($database);
@@ -962,6 +962,7 @@ public function validateCredentialForm(array &$form, FormStateInterface $form_st
 
       // Store the retrieved migration ids in form storage.
       $form_state->set('migrations', $migration_array);
+      $form_state->set('source_base_path', $form_state->getValue('source_base_path'));
 
       // Store the retrived system data in from storage.
       $form_state->set('system_data', $system_data);
@@ -1143,7 +1144,7 @@ public function submitConfirmForm(array &$form, FormStateInterface $form_state)
         'operations' => [
           [
             [MigrateUpgradeRunBatch::class, 'run'],
-            [array_keys($migrations), 'rollback'],
+            [array_keys($migrations), 'rollback', []],
           ],
         ],
         'finished' => [
@@ -1157,13 +1158,14 @@ public function submitConfirmForm(array &$form, FormStateInterface $form_state)
     }
     else {
       $migrations = $storage['migrations'];
+      $config['source_base_path'] = $storage['source_base_path'];
       $batch = [
         'title' => $this->t('Running upgrade'),
         'progress_message' => '',
         'operations' => [
           [
             [MigrateUpgradeRunBatch::class, 'run'],
-            [array_keys($migrations), 'import'],
+            [array_keys($migrations), 'import', $config],
           ],
         ],
         'finished' => [
diff --git a/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php b/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php
index dba824d..46bb33c 100644
--- a/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php
+++ b/core/modules/migrate_drupal_ui/src/MigrateUpgradeRunBatch.php
@@ -65,10 +65,12 @@ class MigrateUpgradeRunBatch {
    *   The full set of migration IDs to import.
    * @param string $operation
    *   The operation to perform, 'import' or 'rollback'.
+   * @param array $config
+   *   An array of additional configuration from the form.
    * @param array $context
    *   The batch context.
    */
-  public static function run($initial_ids, $operation, &$context) {
+  public static function run($initial_ids, $operation, $config, &$context) {
     if (!static::$listenersAdded) {
       $event_dispatcher = \Drupal::service('event_dispatcher');
       if ($operation == 'import') {
@@ -109,6 +111,16 @@ public static function run($initial_ids, $operation, &$context) {
     $migration_id = reset($context['sandbox']['migration_ids']);
     /** @var \Drupal\migrate\Plugin\Migration $migration */
     $migration = \Drupal::service('plugin.manager.migration')->createInstance($migration_id);
+
+    // @TODO, remove this in https://www.drupal.org/node/2681869.
+    $destination = $migration->get('destination');
+    if ($destination['plugin'] === 'entity:file') {
+      // Make sure we have a single trailing slash.
+      $source_base_path = rtrim($config['source_base_path'], '/') . '/';
+      $destination['source_base_path'] = $source_base_path;
+      $migration->set('destination', $destination);
+    }
+
     if ($migration) {
       static::$messages = new MigrateMessageCapture();
       $executable = new MigrateExecutable($migration, static::$messages);
diff --git a/core/modules/migrate_drupal_ui/src/Tests/d6/MigrateUpgrade6Test.php b/core/modules/migrate_drupal_ui/src/Tests/d6/MigrateUpgrade6Test.php
index 597492a..fd4ab62 100644
--- a/core/modules/migrate_drupal_ui/src/Tests/d6/MigrateUpgrade6Test.php
+++ b/core/modules/migrate_drupal_ui/src/Tests/d6/MigrateUpgrade6Test.php
@@ -30,7 +30,7 @@ protected function setUp() {
    * {@inheritdoc}
    */
   protected function getSourceBasePath() {
-    return __DIR__ . '/files';
+    return './';
   }
 
   /**