diff -u b/src/Entity/MediaBundle.php b/src/Entity/MediaBundle.php
--- b/src/Entity/MediaBundle.php
+++ b/src/Entity/MediaBundle.php
@@ -265,29 +265,33 @@
           $entity_type = $field->getTargetEntityTypeId();
           $bundle = $field->getTargetBundle();
 
-          $plugin_definition = \Drupal::service('plugin.manager.field.field_type')
-            ->getDefinition($field->getType());
-
           if ($field->isDisplayConfigurable('form')) {
             $widget = \Drupal::service('plugin.manager.field.widget')
-              ->createInstance($plugin_definition['default_widget'])
-              ->getConfiguration();
+              ->getInstance([
+                'field_definition' => $field,
+                'form_mode' => 'default',
+                'configuration' => [],
+              ]);
 
             entity_get_form_display($entity_type, $bundle, 'default')
               ->setComponent($field->getName(), [
                 'type' => $widget->getPluginId(),
-                'settings' => $widget->getConfiguration(),
+                'settings' => $widget->getSettings(),
               ])
               ->save();
           }
           if ($field->isDisplayConfigurable('view')) {
             $formatter = \Drupal::service('plugin.manager.field.formatter')
-              ->createInstance($plugin_definition['default_formatter']);
+              ->getInstance([
+                'field_definition' => $field,
+                'view_mode' => 'default',
+                'configuration' => [],
+              ]);
 
             entity_get_display($entity_type, $bundle, 'default')
               ->setComponent($field->getName(), [
                 'type' => $formatter->getPluginId(),
-                'settings' => $formatter->getConfiguration(),
+                'settings' => $formatter->getSettings(),
               ])
               ->save();
           }
diff -u b/src/MediaTypeBase.php b/src/MediaTypeBase.php
--- b/src/MediaTypeBase.php
+++ b/src/MediaTypeBase.php
@@ -217,18 +217,19 @@
    *   An appropriate field name that was determined to be available.
    */
   protected function getSourceFieldName() {
-    $base_id = 'media.field_media_' . $this->getPluginId();
+    $base_id = 'field_media_' . $this->getPluginId();
     $tries = 0;
     $storage = $this->entityTypeManager->getStorage('field_storage_config');
 
     // Iterate at least once, until no field with the generated ID is found.
     do {
       $id = $base_id;
-      // If we've tried before, increment and append  suffix.
+      // If we've tried before, increment and append the suffix.
       if ($tries) {
-        $id .= '_' . ++$tries;
+        $id .= '_' . $tries;
       }
-      $field = $storage->load($id);
+      $field = $storage->load('media.' . $id);
+      $tries++;
     }
     while ($field);
 
diff -u b/src/Plugin/MediaEntity/Type/Generic.php b/src/Plugin/MediaEntity/Type/Generic.php
--- b/src/Plugin/MediaEntity/Type/Generic.php
+++ b/src/Plugin/MediaEntity/Type/Generic.php
@@ -43,6 +43,8 @@
    * {@inheritdoc}
    */
   public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    $form = parent::buildConfigurationForm($form, $form_state);
+
     $form['text'] = [
       '#type' => 'markup',
       '#markup' => $this->t("This type provider doesn't need configuration."),
diff -u b/tests/modules/media_entity_test_type/src/Plugin/MediaEntity/Type/TestType.php b/tests/modules/media_entity_test_type/src/Plugin/MediaEntity/Type/TestType.php
--- b/tests/modules/media_entity_test_type/src/Plugin/MediaEntity/Type/TestType.php
+++ b/tests/modules/media_entity_test_type/src/Plugin/MediaEntity/Type/TestType.php
@@ -2,12 +2,7 @@
 
 namespace Drupal\media_entity_test_type\Plugin\MediaEntity\Type;
 
-use Drupal\Core\Entity\Entity\EntityFormDisplay;
-use Drupal\Core\Entity\Entity\EntityViewDisplay;
 use Drupal\Core\Form\FormStateInterface;
-use Drupal\field\Entity\FieldConfig;
-use Drupal\field\Entity\FieldStorageConfig;
-use Drupal\media_entity\MediaTypeSourceFieldTrait;
 use Drupal\media_entity\Plugin\MediaEntity\Type\Generic;
 
 /**
@@ -20,20 +15,6 @@
  * )
  */
 class TestType extends Generic {
-  use MediaTypeSourceFieldTrait;
-
-  /**
-   * {@inheritdoc}
-   */
-  public function sourceFieldInfo() {
-    return [
-      'allowed_types' => ['string'],
-      'default_label' => $this->t('Test source'),
-      'default_type' => 'string',
-      'default_widget' => 'string_textfield',
-      'default_formatter' => 'string',
-    ];
-  }
 
   /**
    * {@inheritdoc}
@@ -49,7 +30,7 @@
    * {@inheritdoc}
    */
   public function defaultConfiguration() {
-    return [
+    return parent::defaultConfiguration() + [
       'test_config_value' => 'This is default value.',
     ];
   }
@@ -58,14 +39,14 @@
    * {@inheritdoc}
    */
   public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    $form = parent::buildConfigurationForm($form, $form_state);
+
     $form['test_config_value'] = [
       '#type' => 'textfield',
       '#title' => $this->t('Test config value'),
       '#default_value' => empty($this->configuration['test_config_value']) ? NULL : $this->configuration['test_config_value'],
     ];
 
-    $form = $this->sourceFieldConfigurationForm($form, $form_state);
-
     $form['source_field']['#description'] = $this->t('Field on media entity that stores the source information.');
 
     return $form;