diff --git a/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstance.php b/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstance.php
index d59906a..f34108c 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstance.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Core/Entity/FieldInstance.php
@@ -89,7 +89,8 @@ class FieldInstance extends ConfigEntityBase implements \ArrayAccess {
    * This will be used as the title of Form API elements for the field in entity
    * edit forms, or as the label for the field values in displayed entities.
    *
-   * If not specified, this defaults to the field_name.
+   * If not specified, this defaults to the field_name (mostly useful for field
+   * instances created in tests).
    *
    * @var string
    */
@@ -267,9 +268,9 @@ public function __construct(array $values, $entity_type = 'field_instance') {
     }
 
     // Set field label to field name if no value has been set.
-    if ($this->label == NULL) {
-      $this->label = $values['field_name'];
-    }
+    $values += array(
+      'label' => $values['field_name'],
+    );
     parent::__construct($values, $entity_type);
   }