diff --git a/modules/simpletest/tests/common.test b/modules/simpletest/tests/common.test
index 177e457..e741ede 100644
--- a/modules/simpletest/tests/common.test
+++ b/modules/simpletest/tests/common.test
@@ -1708,6 +1708,20 @@ class DrupalRenderTestCase extends DrupalWebTestCase {
     ));
   }
 
+  /**
+   * Test rendering elements with invalid keys.
+   */
+  function testDrupalRenderInvalidKeys() {
+    // Define an element with an invalid key.
+    $key = 'not valid';
+    $element = array(
+      $key => 'fail',
+    );
+    $this->drupalSetContent(drupal_render($element));
+    $messages = drupal_get_messages();
+    $this->assertTrue(in_array(t('@key is an invalid render array key.', array('@key' => $key)), $messages['status']), t('Invalid render array keys are skipped.'));
+  }
+
   protected function assertRenderedElement(array $element, $xpath, array $xpath_args = array()) {
     $original_element = $element;
     $this->drupalSetContent(drupal_render($element));