diff --git a/src/Entity/MediaBundle.php b/src/Entity/MediaBundle.php
index 0b16cdd..e7d3295 100644
--- a/src/Entity/MediaBundle.php
+++ b/src/Entity/MediaBundle.php
@@ -255,20 +255,22 @@ class MediaBundle extends ConfigEntityBundleBase implements MediaBundleInterface
     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();
+      $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());
+      $configuration = $instance->getConfiguration();
 
-        if (!empty($default_field['storage'])) {
+      $source_field_info = $instance->getDefaultSourceField();
 
+      if (!$this->isSyncing() && !empty($source_field_info)) {
+
+        foreach ($source_field_info as $source_key => $field_details) {
           // Save the field storage and create the instance.
-          $default_field['storage']->save();
+          $field_details['storage']->save();
           FieldConfig::create([
             'entity_type' => 'media',
-            'field_name' => $default_field['field_name'],
-            'label' => $default_field['label'],
+            'field_name' => $field_details['field_name'],
+            'label' => $field_details['label'],
             'required' => TRUE,
             'bundle' => $this->id(),
           ])->save();
@@ -281,8 +283,8 @@ class MediaBundle extends ConfigEntityBundleBase implements MediaBundleInterface
             'mode' => 'default',
             'status' => TRUE,
           ]);
-          $form_display->setComponent($default_field['field_name'], [
-            'type' => $default_field['field_widget'],
+          $form_display->setComponent($field_details['field_name'], [
+            'type' => $field_details['widget'],
           ])->save();
 
           // Make the field visible on the media entity itself.
@@ -293,13 +295,21 @@ class MediaBundle extends ConfigEntityBundleBase implements MediaBundleInterface
             'mode' => 'default',
             'status' => TRUE,
           ]);
-          $display->setComponent($default_field['field_name'], [
-            'type' => $default_field['field_formatter'],
+          $display->setComponent($field_details['field_name'], [
+            'type' => $field_details['formatter'],
           ])->save();
 
+          $configuration[$source_key] = $field_details['field_name'];
         }
 
+        // Save the source field(s) name(s) to the plugin type configuration.
+        \Drupal::configFactory()
+          ->getEditable('media_entity.bundle.' . $this->id())
+          ->set('type_configuration', $configuration)
+          ->save();
+
       }
+
     }
 
   }
diff --git a/src/MediaTypeInterface.php b/src/MediaTypeInterface.php
index 32a49e5..47e6994 100644
--- a/src/MediaTypeInterface.php
+++ b/src/MediaTypeInterface.php
@@ -88,22 +88,28 @@ interface MediaTypeInterface extends PluginInspectionInterface, ConfigurablePlug
   /**
    * Provide a default source field.
    *
-   * Plugins defining media bundles are suggested to implement this method and
-   * create a field that will be used as default source field, on bundle
-   * creation. Make sure this method returns unsaved entities, once these are
-   * only going to be saved and used if the user marked the option to use the
-   * default field provided.
+   * Plugins defining media bundles are required to implement this method and
+   * create at least one (unsaved) field that will be used as default source
+   * field(s), on bundle creation.
    *
    * @return array
-   *   An associative array containing the following keys:
-   *   'storage' => \Drupal\field\Entity\FieldStorageConfig A config entity for
-   *   this field storage.
+   *   An associative array of fields that this plugin considers as source
+   *   fields, keyed by the string used in the configuration form to reference
+   *   this/these field(s). In a typical scenario, the array will contain only
+   *   one value, and this first-level key will likely be "source_field". Other
+   *   plugins could refer to their source fields with keys such as
+   *   "main_source_field" + "secondary_source_field" or anything similar.
+   *   Each value of this array will also be an associative array with the
+   *   following structure:
+   *   'storage' => \Drupal\field\Entity\FieldStorageConfig An unsaved 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.
-   *   'field_widget' => (string) The id of the widget to use.
-   *   'field_formatter' => (string) The id of the formatter to use.
+   *   'widget' => (string) The id of the widget to use.
+   *   'formatter' => (string) The id of the formatter to use.
+   *
    *   Note that the storage config entity need to be returned unsaved, and the
-   *   main form will be responsible for saving them.
+   *   main form will be responsible for saving it when processing the submit.
    */
   public function getDefaultSourceField();