diff -u b/core/modules/media/src/Entity/Media.php b/core/modules/media/src/Entity/Media.php
--- b/core/modules/media/src/Entity/Media.php
+++ b/core/modules/media/src/Entity/Media.php
@@ -174,7 +174,7 @@
       $this->thumbnail->alt = $media_source->getMetadata($this, $plugin_definition['thumbnail_alt_metadata_attribute']);
     }
     else {
-      $this->thumbnail->alt = $this->t('Thumbnail', [], ['options' => $this->langcode->value]);
+      $this->thumbnail->alt = $this->t('Thumbnail', [], ['langcode' => $this->langcode->value]);
     }
 
     // Set the thumbnail title.
diff -u b/core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestTranslation.php b/core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestTranslation.php
--- b/core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestTranslation.php
+++ b/core/modules/media/tests/modules/media_test_source/src/Plugin/media/Source/TestTranslation.php
@@ -12,6 +12,7 @@
  *   label = @Translation("Test source with translations"),
  *   description = @Translation("Test media source with translations."),
  *   allowed_field_types = {"string"},
+ *   thumbnail_alt_metadata_attribute = "test_thumbnail_alt",
  * )
  */
 class TestTranslation extends Test {
@@ -24,6 +25,11 @@
       return 'public://' . $media->language()->getId() . '.png';
     }
 
+    if ($attribute_name == 'test_thumbnail_alt') {
+      $langcode = $media->language()->getId();
+      return $this->t('Test Thumbnail ' . $langcode, [], ['langcode' => $langcode]);
+    }
+
     return parent::getMetadata($media, $attribute_name);
   }
 
diff -u b/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php b/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php
--- b/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php
+++ b/core/modules/media/tests/src/Functional/MediaTemplateSuggestionsTest.php
@@ -37,7 +37,7 @@
     $view_mode = 'full';
 
     // Simulate theming of the media item.
-    $build = \Drupal::entityManager()->getViewBuilder('media')->view($media, $view_mode);
+    $build = \Drupal::entityTypeManager()->getViewBuilder('media')->view($media, $view_mode);
 
     $variables['elements'] = $build;
     $suggestions = \Drupal::moduleHandler()->invokeAll('theme_suggestions_media', [$variables]);
diff -u b/core/modules/media/tests/src/Kernel/MediaTranslationTest.php b/core/modules/media/tests/src/Kernel/MediaTranslationTest.php
--- b/core/modules/media/tests/src/Kernel/MediaTranslationTest.php
+++ b/core/modules/media/tests/src/Kernel/MediaTranslationTest.php
@@ -94,6 +94,9 @@
       }
       $this->assertTrue($result, new FormattableMarkup('%language translation field value not correct.', ['%language' => $langcode]));
       $this->assertEquals('public://' . $langcode . '.png', $media_translation->getSource()->getMetadata($media_translation, 'thumbnail_uri'), new FormattableMarkup('%language translation thumbnail metadata attribute is not correct.', ['%language' => $langcode]));
+      $this->assertEquals('public://' . $langcode . '.png', $media_translation->get('thumbnail')->entity->getFileUri(), new FormattableMarkup('%language translation thumbnail metadata attribute is not correct.', ['%language' => $langcode]));
+      $this->assertEquals('Test Thumbnail ' . $langcode, $media_translation->getSource()->getMetadata($media_translation, 'test_thumbnail_alt'));
+      $this->assertEquals('Test Thumbnail ' . $langcode, $media_translation->get('thumbnail')->alt);
     }
   }