diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index 64300e7..04b90e5 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -675,10 +675,8 @@ public function prepareForm($form_id, &$form, &$form_state) {
 
     $form += $this->getElementInfo('form');
     $form += array('#tree' => FALSE, '#parents' => array());
-    if (isset($form_state['build_info']['callback_object'])) {
-      $form['#validate'][] = array($form_state['build_info']['callback_object'], 'validateForm');
-      $form['#submit'][] = array($form_state['build_info']['callback_object'], 'submitForm');
-    }
+    $form['#validate'][] = array($form_state['build_info']['callback_object'], 'validateForm');
+    $form['#submit'][] = array($form_state['build_info']['callback_object'], 'submitForm');
 
     // If no #theme has been set, automatically apply theme suggestions.
     // theme_form() itself is in #theme_wrappers and not #theme. Therefore, the
diff --git a/core/modules/field/src/Tests/FieldAttachOtherTest.php b/core/modules/field/src/Tests/FieldAttachOtherTest.php
index a058dd6..379d108 100644
--- a/core/modules/field/src/Tests/FieldAttachOtherTest.php
+++ b/core/modules/field/src/Tests/FieldAttachOtherTest.php
@@ -342,6 +342,7 @@ function testEntityFormDisplayExtractFormValues() {
     $values_2[1]['value'] = 0;
 
     // Pretend the form has been built.
+    $form_state['build_info']['callback_object'] = \Drupal::entityManager()->getFormObject($entity_type, 'default');
     \Drupal::formBuilder()->prepareForm('field_test_entity_form', $form, $form_state);
     drupal_process_form('field_test_entity_form', $form, $form_state);
     $form_state['values'][$this->field_name] = $values;
diff --git a/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php b/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
index 30380ac..b0ce2f8 100644
--- a/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
+++ b/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
@@ -216,6 +216,7 @@ private function formSubmitHelper($form, $edit) {
 
     $form_state['input'] = $edit;
     $form_state['input']['form_id'] = $form_id;
+    $form_state['build_info']['callback_object'] = new StubForm($form_id, $form);
 
     \Drupal::formBuilder()->prepareForm($form_id, $form, $form_state);
 
diff --git a/core/modules/system/src/Tests/Form/FormTest.php b/core/modules/system/src/Tests/Form/FormTest.php
index f113bcf..2b4850e 100644
--- a/core/modules/system/src/Tests/Form/FormTest.php
+++ b/core/modules/system/src/Tests/Form/FormTest.php
@@ -109,6 +109,7 @@ function testRequiredFields() {
           $form[$element]['#required'] = $required;
           $form_state['input'][$element] = $empty;
           $form_state['input']['form_id'] = $form_id;
+          $form_state['build_info']['callback_object'] = new StubForm($form_id, $form);
           $form_state['method'] = 'post';
           // The form token CSRF protection should not interfere with this test,
           // so we bypass it by setting the token to FALSE.
diff --git a/core/modules/system/src/Tests/Form/StubForm.php b/core/modules/system/src/Tests/Form/StubForm.php
new file mode 100644
index 0000000..225371b
--- /dev/null
+++ b/core/modules/system/src/Tests/Form/StubForm.php
@@ -0,0 +1,64 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Form\StubForm.
+ */
+
+namespace Drupal\system\Tests\Form;
+
+use Drupal\Core\Form\FormBase;
+
+/**
+ * Provides a stub form for testing purposes.
+ */
+class StubForm extends FormBase {
+
+  /**
+   * The form array.
+   *
+   * @var array
+   */
+  protected $form;
+
+  /**
+   * The form ID.
+   *
+   * @var string
+   */
+  protected $formId;
+
+  /**
+   * Constructs a StubForm.
+   *
+   * @param string $form_id
+   *   The form ID.
+   * @param array $form
+   *   The form array.
+   */
+  public function __construct($form_id, $form) {
+    $this->formId = $form_id;
+    $this->form = $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    $this->formId;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, array &$form_state) {
+    return $this->form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, array &$form_state) {
+  }
+
+}