diff -u b/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php b/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php
--- b/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Serialization/EntitySerializationTest.php
@@ -138,7 +138,7 @@
'langcode' => '' . LANGUAGE_NOT_SPECIFIED . '',
'default_langcode' => '',
'name' => '' . $this->values['name'] . '',
- 'user_id' => '' . $this->values['user_id'] . '',
+ 'user_id' => '' . $this->values['user_id'] . '',
'field_test_text' => '' . $this->values['field_test_text']['value'] . '' . $this->values['field_test_text']['format'] . '',
);
// Sort it in the same order as normalised.