diff --git a/core/tests/Drupal/Tests/Core/File/MimeTypeGuesserTest.php b/core/tests/Drupal/Tests/Core/File/MimeTypeGuesserTest.php
index 154c3ec..1c96ef5 100644
--- a/core/tests/Drupal/Tests/Core/File/MimeTypeGuesserTest.php
+++ b/core/tests/Drupal/Tests/Core/File/MimeTypeGuesserTest.php
@@ -24,26 +24,24 @@ class MimeTypeGuesserTest extends UnitTestCase {
    * @see Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesser
    */
   public function testSymfonyGuesserRegistration() {
-    // Make the guessers property accessible on Symfony's MimeTypeGuesser.
-    $symfony_guesser = SymfonyMimeTypeGuesser::getInstance();
     // Test that the Drupal mime type guess is not being used before the
     // override method is called. It is possible that the test environment does
     // not support the default guessers.
-    $guessers = $this->readAttribute($symfony_guesser, 'guessers');
+    $guessers = $this->readAttribute(SymfonyMimeTypeGuesser::getInstance(), 'guessers');
     if (count($guessers)) {
       $this->assertNotInstanceOf('Drupal\Core\File\MimeType\MimeTypeGuesser', $guessers[0]);
     }
     $container = new ContainerBuilder();
     $container->set('file.mime_type.guesser', new MimeTypeGuesser());
     MimeTypeGuesser::registerWithSymfonyGuesser($container);
-    $guessers = $this->readAttribute($symfony_guesser, 'guessers');
+    $guessers = $this->readAttribute(SymfonyMimeTypeGuesser::getInstance(), 'guessers');
     $this->assertInstanceOf('Drupal\Core\File\MimeType\MimeTypeGuesser', $guessers[0]);
     $count = count($guessers);
 
     $container = new ContainerBuilder();
     $container->set('file.mime_type.guesser', new MimeTypeGuesser());
     MimeTypeGuesser::registerWithSymfonyGuesser($container);
-    $guessers = $this->readAttribute($symfony_guesser, 'guessers');
+    $guessers = $this->readAttribute(SymfonyMimeTypeGuesser::getInstance(), 'guessers');
     $this->assertInstanceOf('Drupal\Core\File\MimeType\MimeTypeGuesser', $guessers[0]);
     $new_count = count($guessers);
     $this->assertEquals($count, $new_count, 'The count of mime type guessers remains the same after container re-init.');