diff --git a/core/modules/file/src/Controller/FileUploadController.php b/core/modules/file/src/Controller/FileUploadController.php
index 0c9c6545b2..0bbc8e00e5 100644
--- a/core/modules/file/src/Controller/FileUploadController.php
+++ b/core/modules/file/src/Controller/FileUploadController.php
@@ -56,6 +56,9 @@ public function upload(Request $request, FileInterface $file) {
 
     $this->streamUploadData($file);
 
+    // Save the file so file size is re-calculated.
+    $file->save();
+
     return new Response('OK');
   }
 
diff --git a/core/modules/file/tests/src/Kernel/FileUploadTest.php b/core/modules/file/tests/src/Kernel/FileUploadTest.php
new file mode 100644
index 0000000000..1e136c225e
--- /dev/null
+++ b/core/modules/file/tests/src/Kernel/FileUploadTest.php
@@ -0,0 +1,115 @@
+<?php
+
+namespace Drupal\Tests\file\Kernel;
+
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\file\Entity\File;
+use Drupal\user\Entity\User;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Tests binary data file upload route.
+ *
+ * @group file
+ */
+class FileUploadTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['file', 'user', 'system'];
+
+  /**
+   * Created file entity.
+   *
+   * @var \Drupal\file\Entity\File
+   */
+  protected $file;
+
+  /**
+   * An authenticated user.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $user;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->installEntitySchema('file');
+    $this->installEntitySchema('user');
+    $this->installSchema('file', ['file_usage']);
+    $this->installSchema('system', 'sequences');
+
+    // Create a file so binary data uploading can be used on it.
+    file_put_contents('public://example.txt', 'TEST');
+
+    // Create a user to use as the file owner.
+    $this->user = User::create([
+      'name' => 'user1',
+      'status' => 1,
+    ]);
+    $this->user->save();
+
+    $this->file = File::create([
+      'uid' => $this->user->id(),
+      'uri' => 'public://example.txt',
+    ]);
+
+    $this->file->save();
+  }
+
+  /**
+   * Tests using the file upload route.
+   */
+  public function testFileUploadString() {
+    $new_file_data = 'TEST WITH NEW DATA';
+    $uri = '/file/upload/' . $this->file->id();
+
+    $request = Request::create($uri, 'POST', [], [], [], [], $new_file_data);
+
+    // Set the file owner as the current user.
+    $this->container->get('current_user')->setAccount($this->user);
+
+    $response = $this->container->get('http_kernel')->handle($request);
+
+    $this->assertSame(415, $response->getStatusCode());
+
+    // Now set the correct Content-Type header.
+    $request->headers->set('Content-Type', 'application/octet-stream');
+
+    $response = $this->container->get('http_kernel')->handle($request);
+
+    $this->assertSame(200, $response->getStatusCode());
+    $this->assertSame('OK', $response->getContent());
+    $this->assertSame($new_file_data, file_get_contents('public://example.txt'));
+  }
+
+  /**
+   * Tests using the file upload route.
+   */
+  public function testFileUploadBinary() {
+    $uri = '/file/upload/' . $this->file->id();
+
+    $new_binary_data = '';
+
+    $request = Request::create($uri, 'POST', [], [], [], [], $new_binary_data);
+
+    // Set the file owner as the current user.
+    $this->container->get('current_user')->setAccount($this->user);
+
+    $request->headers->set('Content-Type', 'application/octet-stream');
+
+    $response = $this->container->get('http_kernel')->handle($request);
+
+    $this->assertSame(200, $response->getStatusCode());
+    $this->assertSame('OK', $response->getContent());
+    $this->assertSame($new_binary_data, file_get_contents('public://example.txt'));
+  }
+
+}