diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index c0a59e0..256b29c 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -1078,6 +1078,11 @@ protected function drupalGet($path, array $options = array(), array $headers = a
     $out = $this->curlExec(array(CURLOPT_HTTPGET => TRUE, CURLOPT_URL => url($path, $options), CURLOPT_NOBODY => FALSE, CURLOPT_HTTPHEADER => $headers));
     $this->refreshVariables(); // Ensure that any changes to variables in the other thread are picked up.
 
+    // Fail if the page returns an error.
+    if ((string) current($this->xpath('//title')) == 'Error') {
+      $this->fail('Page returned an error.');
+    }
+
     // Replace original page output with new output from redirected page(s).
     if ($new = $this->checkForMetaRefresh()) {
       $out = $new;