diff --git a/media_entity.module b/media_entity.module
index f06bc00..9b157e5 100644
--- a/media_entity.module
+++ b/media_entity.module
@@ -6,7 +6,6 @@
  */
 
 use Drupal\Core\Routing\RouteMatchInterface;
-use Drupal\field\Entity\FieldConfig;
 use Drupal\media_entity\Entity\MediaBundle;
 
 /**
@@ -84,36 +83,3 @@ function media_entity_copy_icons($source, $destination) {
     }
   }
 }
-
-/**
- * Implements hook_ENTITY_TYPE_insert().
- */
-function media_entity_media_bundle_insert(MediaBundle $media_bundle) {
-  // When creating new bundles, add also a source field, if configured to do so.
-  if (!$media_bundle->isSyncing() && empty($media_bundle->getTypeConfiguration()['source_field']) && $media_bundle->getCreateSourceField()) {
-    $media_type_manager = \Drupal::service('plugin.manager.media_entity.type');
-    $instance = $media_type_manager->createInstance($media_bundle->getType()->getPluginId(), $media_bundle->getTypeConfiguration());
-    $default_field = $instance->getDefaultSourceField();
-    if (!empty($default_field['storage'])) {
-      // Save the field storage and create the instance.
-      $default_field['storage']->save();
-      FieldConfig::create([
-        'entity_type' => 'media',
-        'field_name' => $default_field['field_name'],
-        'label' => $default_field['label'],
-        'required' => TRUE,
-        'bundle' => $media_bundle->id(),
-      ])->save();
-      // Make the field visible on the form display.
-      $form_display = entity_get_form_display('media', $media_bundle->id(), 'default');
-      $form_display->setComponent($default_field['field_name'], [
-        'type' => $default_field['field_widget'],
-      ])->save();
-      // Make the field visible on the media entity itself.
-      $display = entity_get_display('media', $media_bundle->id(), 'default');
-      $display->setComponent($default_field['field_name'], [
-        'type' => $default_field['field_formatter'],
-      ])->save();
-    }
-  }
-}
diff --git a/src/Entity/MediaBundle.php b/src/Entity/MediaBundle.php
index 5227d50..277f53a 100644
--- a/src/Entity/MediaBundle.php
+++ b/src/Entity/MediaBundle.php
@@ -4,10 +4,12 @@ namespace Drupal\media_entity\Entity;
 
 use Drupal\Core\Config\Entity\ConfigEntityBundleBase;
 use Drupal\Core\Entity\EntityDescriptionInterface;
+use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Entity\EntityWithPluginCollectionInterface;
 use Drupal\Core\Plugin\DefaultSingleLazyPluginCollection;
 use Drupal\media_entity\MediaBundleInterface;
 use Drupal\media_entity\MediaInterface;
+use Drupal\field\Entity\FieldConfig;
 
 /**
  * Defines the Media bundle configuration entity.
@@ -127,13 +129,6 @@ class MediaBundle extends ConfigEntityBundleBase implements MediaBundleInterface
   public $status = TRUE;
 
   /**
-   * A flag indicating if we should create a source field upon save.
-   *
-   * @var bool
-   */
-  public $create_source_field = TRUE;
-
-  /**
    * {@inheritdoc}
    */
   public function id() {
@@ -238,22 +233,59 @@ class MediaBundle extends ConfigEntityBundleBase implements MediaBundleInterface
   /**
    * {@inheritdoc}
    */
-  public function getCreateSourceField() {
-    return $this->create_source_field;
+  public function shouldCreateNewRevision() {
+    return $this->new_revision;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function shouldCreateNewRevision() {
-    return $this->new_revision;
+  public function setNewRevision($new_revision) {
+    $this->new_revision = $new_revision;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function setNewRevision($new_revision) {
-    $this->new_revision = $new_revision;
+  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
+    parent::postSave($storage, $update);
+
+    if (!$update) {
+      // When creating new bundles, add also a source field, if configured to
+      // do so.
+      if (!$this->isSyncing() && empty($this->getTypeConfiguration()['source_field']) && !empty($this->getTypeConfiguration()['create_source_field'])) {
+        $media_type_manager = \Drupal::service('plugin.manager.media_entity.type');
+        /** @var \Drupal\media_entity\MediaTypeInterface $instance */
+        $instance = $media_type_manager->createInstance($this->getType()->getPluginId(), $this->getTypeConfiguration());
+        $default_field = $instance->getDefaultSourceField();
+
+        if (!empty($default_field['storage'])) {
+          // Save the field storage and create the instance.
+          $default_field['storage']->save();
+          FieldConfig::create([
+            'entity_type' => 'media',
+            'field_name' => $default_field['field_name'],
+            'label' => $default_field['label'],
+            'required' => TRUE,
+            'bundle' => $this->id(),
+          ])->save();
+
+          // Make the field visible on the form display.
+          $form_display = entity_get_form_display('media', $this->id(), 'default');
+          $form_display->setComponent($default_field['field_name'], [
+            'type' => $default_field['field_widget'],
+          ])->save();
+
+          // Make the field visible on the media entity itself.
+          $display = entity_get_display('media', $this->id(), 'default');
+          $display->setComponent($default_field['field_name'], [
+            'type' => $default_field['field_formatter'],
+          ])->save();
+        }
+
+      }
+    }
+
   }
 
 }
diff --git a/src/MediaBundleForm.php b/src/MediaBundleForm.php
index c11c83e..6ae83bb 100644
--- a/src/MediaBundleForm.php
+++ b/src/MediaBundleForm.php
@@ -170,22 +170,6 @@ class MediaBundleForm extends EntityForm {
       $form['type_configuration'][$plugin->getPluginId()] += $instance->buildConfigurationForm([], $form_state);
     }
 
-    // Add a checkbox to allow the field being created automattically on save.
-    if (!empty($form['type_configuration'][$plugin->getPluginId()]['source_field']) && empty($plugin_configuration['source_field'])) {
-      $has_source_field_options = !empty($form['type_configuration'][$plugin->getPluginId()]['source_field']['#options']);
-      $form['type_configuration'][$plugin->getPluginId()]['create_source_field'] = [
-        '#type' => 'checkbox',
-        '#title' => $this->t('Create source field automatically when saving this form.'),
-        '#description' => $this->t('If checked, a default field will be created and used as a source field. You can change this setting later on.'),
-        '#default_value' => $bundle->getCreateSourceField(),
-        // Try to place this checkbox close to the sourcefield select element.
-        '#weight' => !empty($form['type_configuration'][$plugin->getPluginId()]['source_field']['#weight']) ? $form['type_configuration'][$plugin->getPluginId()]['source_field']['#weight'] + 0.01 : -2,
-        '#access' => !$has_source_field_options,
-      ];
-      // If there are no options, the dropdown is meaningless.
-      $form['type_configuration'][$plugin->getPluginId()]['source_field']['#access'] = $has_source_field_options || !$bundle->getCreateSourceField();
-    }
-
     // Field mapping configuration.
     $form['field_mapping'] = [
       '#type' => 'fieldset',
diff --git a/src/MediaBundleInterface.php b/src/MediaBundleInterface.php
index 6bc850a..97e02f9 100644
--- a/src/MediaBundleInterface.php
+++ b/src/MediaBundleInterface.php
@@ -89,14 +89,6 @@ interface MediaBundleInterface extends ConfigEntityInterface, RevisionableEntity
   public function getStatus();
 
   /**
-   * Returns the flag that indicate if a source field should be auto-created.
-   *
-   * @return bool
-   *   TRUE if the field should be created when saving the bundle.
-   */
-  public function getCreateSourceField();
-
-  /**
    * Sets whether a new revision should be created by default.
    *
    * @param bool $new_revision
diff --git a/src/MediaTypeInterface.php b/src/MediaTypeInterface.php
index 9e84257..32a49e5 100644
--- a/src/MediaTypeInterface.php
+++ b/src/MediaTypeInterface.php
@@ -96,7 +96,7 @@ interface MediaTypeInterface extends PluginInspectionInterface, ConfigurablePlug
    *
    * @return array
    *   An associative array containing the following keys:
-   *   'config' => \Drupal\field\Entity\FieldStorageConfig A config entity for
+   *   'storage' => \Drupal\field\Entity\FieldStorageConfig A config entity for
    *   this field storage.
    *   'field_name' => (string) The name to be used for the field instance.
    *   'label' => (string) The label to be used for the field instance.