diff --git a/core/lib/Drupal/Core/Render/Element/Radio.php b/core/lib/Drupal/Core/Render/Element/Radio.php
index 2e8b28c..501da61 100644
--- a/core/lib/Drupal/Core/Render/Element/Radio.php
+++ b/core/lib/Drupal/Core/Render/Element/Radio.php
@@ -61,8 +61,19 @@ public static function preRenderRadio($element) {
     $element['#attributes']['type'] = 'radio';
     Element::setAttributes($element, array('id', 'name', '#return_value' => 'value'));
 
-    if (isset($element['#return_value']) && $element['#value'] !== FALSE && $element['#value'] == $element['#return_value']) {
-      $element['#attributes']['checked'] = 'checked';
+    if (isset($element['#return_value']) && $element['#value'] !== FALSE) {
+      // To avoid auto-casting during '==' we convert int 0 to '0' for both
+      // operands. It will prevent wrong true-checking for both cases: 0 ==
+      // 'string' and 'string' == 0.
+      if ($element['#value'] === 0) {
+        $element['#value'] = '0';
+      }
+      if ($element['#return_value'] === 0) {
+        $element['#return_value'] = '0';
+      }
+      if ($element['#value'] == $element['#return_value']) {
+        $element['#attributes']['checked'] = 'checked';
+      }
     }
     static::setAttributes($element, array('form-radio'));
 
diff --git a/core/modules/system/src/Tests/Form/ElementTest.php b/core/modules/system/src/Tests/Form/ElementTest.php
index 1cc6cd8..249ad5e 100644
--- a/core/modules/system/src/Tests/Form/ElementTest.php
+++ b/core/modules/system/src/Tests/Form/ElementTest.php
@@ -94,6 +94,20 @@ function testOptions() {
   }
 
   /**
+   * Tests correct checked attribute for radios element.
+   */
+  function testRadiosChecked() {
+    // Verify that there is only one radio option checked.
+    $this->drupalGet('form-test/radios-checked');
+    $elements = $this->xpath('//input[@name="radios" and @checked]');
+    $this->assertEqual(count($elements), 1);
+    $this->assertIdentical((string) $elements[0]['value'], '0');
+    $elements = $this->xpath('//input[@name="radios-string" and @checked]');
+    $this->assertEqual(count($elements), 1);
+    $this->assertIdentical((string) $elements[0]['value'], 'bar');
+  }
+
+  /**
    * Tests wrapper ids for checkboxes and radios.
    */
   function testWrapperIds() {
diff --git a/core/modules/system/tests/modules/form_test/form_test.routing.yml b/core/modules/system/tests/modules/form_test/form_test.routing.yml
index d8c5833..9a595d7 100644
--- a/core/modules/system/tests/modules/form_test/form_test.routing.yml
+++ b/core/modules/system/tests/modules/form_test/form_test.routing.yml
@@ -294,6 +294,14 @@ form_test.checkboxes_radios:
   requirements:
     _access: 'TRUE'
 
+form_test.radios_checked:
+  path: '/form-test/radios-checked'
+  defaults:
+    _form: '\Drupal\form_test\Form\FormTestRadiosCheckedForm'
+    _title: 'Radios checked defalt value'
+  requirements:
+    _access: 'TRUE'
+
 form_test.email:
   path: '/form-test/email'
   defaults:
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestRadiosCheckedForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestRadiosCheckedForm.php
new file mode 100644
index 0000000..e7e594e
--- /dev/null
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestRadiosCheckedForm.php
@@ -0,0 +1,67 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\form_test\Form\FormTestRadiosCheckedForm.
+ */
+
+namespace Drupal\form_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Symfony\Component\HttpFoundation\JsonResponse;
+
+/**
+ * Form constructor to test #default_value settings of radios.
+ */
+class FormTestRadiosCheckedForm extends FormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'form_test_radios_checked';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $form['radios'] = array(
+      '#type' => 'radios',
+      '#title' => 'Radios',
+      '#options' => array(
+        0 => 'Zero',
+        'foo' => 'Foo',
+        1 => 'One',
+        'bar' => '<em>Bar - radios</em>',
+        '>' => "<em>Special Char</em><script>alert('radios');</script>",
+      ),
+      '#default_value' => 0,
+    );
+    $form['radios-string'] = array(
+      '#type' => 'radios',
+      '#title' => 'Radios',
+      '#options' => array(
+        0 => 'Zero',
+        'foo' => 'Foo',
+        1 => 'One',
+        'bar' => '<em>Bar - radios</em>',
+        '>' => "<em>Special Char</em><script>alert('radios');</script>",
+      ),
+      '#default_value' => 'bar',
+    );
+
+    $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $form_state->setResponse(new JsonResponse($form_state->getValues()));
+  }
+
+}
diff --git a/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
index 1d18ee1..cc49773 100644
--- a/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
+++ b/core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
@@ -1706,7 +1706,7 @@ public function buildOptionsForm(&$form, FormStateInterface $form_state) {
         break;
       case 'link_display':
         $form['#title'] .= $this->t('Which display to use for path');
-        $options = array(FALSE => $this->t('None'), 'custom_url' => $this->t('Custom URL'));
+        $options = array('' => $this->t('None'), 'custom_url' => $this->t('Custom URL'));
 
         foreach ($this->view->storage->get('display') as $display_id => $display) {
           if ($this->view->displayHandlers->get($display_id)->hasPath()) {
diff --git a/core/modules/views_ui/src/Tests/DisplayTest.php b/core/modules/views_ui/src/Tests/DisplayTest.php
index 4fab7d8..0451045 100644
--- a/core/modules/views_ui/src/Tests/DisplayTest.php
+++ b/core/modules/views_ui/src/Tests/DisplayTest.php
@@ -168,7 +168,9 @@ public function testLinkDisplay() {
     $this->assertEqual($result[0], t('None'), 'Make sure that the link option summary shows "None" by default.');
 
     $this->drupalGet($link_display_path);
-    $this->assertFieldChecked('edit-link-display-0');
+    // We are looking for the None option which has a '' key, that's why there
+    // is no key appended in the ID.
+    $this->assertFieldChecked('edit-link-display-');
 
     // Test the default radio option on the link display form.
     $this->drupalPostForm($link_display_path, array('link_display' => 'page_1'), t('Apply'));