diff --git a/core/lib/Drupal/Core/Render/Element/Radio.php b/core/lib/Drupal/Core/Render/Element/Radio.php
index 2e8b28c..8036952 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'));