diff -u b/core/modules/media/src/MediaTypeForm.php b/core/modules/media/src/MediaTypeForm.php
--- b/core/modules/media/src/MediaTypeForm.php
+++ b/core/modules/media/src/MediaTypeForm.php
@@ -367,7 +367,7 @@
   }
 
   /**
-   * Sets source display options to an entity display.
+   * Sets source display options on an entity display.
    *
    * @param \Drupal\Core\Entity\Display\EntityDisplayInterface $entity_display
    *   A entity display.
diff -u b/core/modules/media/tests/src/Kernel/MediaSourceTest.php b/core/modules/media/tests/src/Kernel/MediaSourceTest.php
--- b/core/modules/media/tests/src/Kernel/MediaSourceTest.php
+++ b/core/modules/media/tests/src/Kernel/MediaSourceTest.php
@@ -7,7 +7,6 @@
 use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\media\Entity\Media;
 use Drupal\media\Entity\MediaType;
-use Drupal\media\MediaTypeForm;
 
 /**
  * Tests media source plugins related logic.
@@ -484,14 +483,14 @@
   /**
    * Creates a media type via form submit.
    *
-   * @param int $media_type_id
-   *   Media type id.
+   * @param int $source_plugin_id
+   *   Source plugin ID.
    * @param string $field_name
    *   Source field name.
    */
-  protected function createMediaTypeViaForm($media_type_id, $field_name) {
+  protected function createMediaTypeViaForm($source_plugin_id, $field_name) {
     /** @var \Drupal\media\MediaTypeInterface $type */
-    $type = MediaType::create(['source' => $media_type_id]);
+    $type = MediaType::create(['source' => $source_plugin_id]);
 
     $form = $this->container->get('entity_type.manager')
       ->getFormObject('media_type', 'add')
@@ -500,7 +499,7 @@
     $form_state = new FormState();
     $form_state->setValues([
       'label' => 'Test type',
-      'id' => $media_type_id,
+      'id' => $source_plugin_id,
       'op' => t('Save'),
     ]);
 
@@ -508,13 +507,13 @@
     $field_manager = \Drupal::service('entity_field.manager');
 
     // Source field not created yet.
-    $fields = $field_manager->getFieldDefinitions('media', $media_type_id);
+    $fields = $field_manager->getFieldDefinitions('media', $source_plugin_id);
     $this->assertArrayNotHasKey($field_name, $fields);
 
     \Drupal::formBuilder()->submitForm($form, $form_state);
 
     // Source field exists now.
-    $fields = $field_manager->getFieldDefinitions('media', $media_type_id);
+    $fields = $field_manager->getFieldDefinitions('media', $source_plugin_id);
     $this->assertArrayHasKey($field_name, $fields);
   }