core/modules/file/src/Entity/File.php              | 31 ++++++++++++++++++++++
 .../EntityResource/Media/MediaResourceTestBase.php |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/core/modules/file/src/Entity/File.php b/core/modules/file/src/Entity/File.php
index a9ade9e..dee25ab 100644
--- a/core/modules/file/src/Entity/File.php
+++ b/core/modules/file/src/Entity/File.php
@@ -7,6 +7,7 @@
 use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\Url;
 use Drupal\file\FileInterface;
 use Drupal\user\UserInterface;
 
@@ -71,12 +72,42 @@ public function setFileUri($uri) {
    * @see file_url_transform_relative()
    */
   public function url($rel = 'canonical', $options = []) {
+    // @todo Remove this work-around before Drupal 9.0.0. This was introduced as
+    // a temporary work-around in https://www.drupal.org/node/2277705 to provide
+    // REST support for file entities. https://www.drupal.org/node/2825487 makes
+    // this obsolete.
     return file_create_url($this->getFileUri());
   }
 
   /**
    * {@inheritdoc}
    */
+  public function toUrl($rel = 'canonical', array $options = []) {
+    // Lie because we must provide BC.
+    // @see ::url()
+    // @todo Remove in https://www.drupal.org/node/2825487.
+    if ($rel === 'canonical') {
+      return Url::fromUri($this->url());
+    }
+    return parent::toUrl($rel, $options);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasLinkTemplate($rel) {
+    // Lie because we must provide BC.
+    // @see ::url()
+    // @todo Remove in https://www.drupal.org/node/2825487.
+    if ($rel === 'canonical') {
+      return TRUE;
+    }
+    return parent::hasLinkTemplate($rel);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function getMimeType() {
     return $this->get('filemime')->value;
   }
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php
index 3de224a..475a1ca 100644
--- a/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Media/MediaResourceTestBase.php
@@ -154,6 +154,7 @@ protected function getExpectedNormalizedEntity() {
           'target_id' => (int) $file->id(),
           'target_type' => 'file',
           'target_uuid' => $file->uuid(),
+          'url' => $file->url(),
         ],
       ],
       'thumbnail' => [
@@ -165,6 +166,7 @@ protected function getExpectedNormalizedEntity() {
           'target_type' => 'file',
           'target_uuid' => $thumbnail->uuid(),
           'title' => 'Llama',
+          'url' => $thumbnail->url(),
         ],
       ],
       'status' => [