diff --git a/core/modules/simpletest/drupal_web_test_case.php b/core/modules/simpletest/drupal_web_test_case.php
index 9d993d4..9fab2dd 100644
--- a/core/modules/simpletest/drupal_web_test_case.php
+++ b/core/modules/simpletest/drupal_web_test_case.php
@@ -1833,7 +1833,7 @@ class DrupalWebTestCase extends DrupalTestCase {
         $submit_matches = $this->handleForm($post, $edit, $upload, $ajax ? NULL : $submit, $form);
         $action = isset($form['action']) ? $this->getAbsoluteUrl((string) $form['action']) : $this->getUrl();
         if ($ajax) {
-          $action = $this->getAbsoluteUrl(!empty($submit['path']) ? $submit['path'] : 'system/ajax');
+          $action = $this->getAbsoluteUrl(!empty($submit['path']) ? $submit['path'] : url('system/ajax'));
           // Ajax callbacks verify the triggering element if necessary, so while
           // we may eventually want extra code that verifies it in the
           // handleForm() function, it's not currently a requirement.
@@ -1982,7 +1982,10 @@ class DrupalWebTestCase extends DrupalTestCase {
     // Unless a particular path is specified, use the one specified by the
     // Ajax settings, or else 'system/ajax'.
     if (!isset($ajax_path)) {
-      $ajax_path = isset($ajax_settings['url']) ? $ajax_settings['url'] : 'system/ajax';
+      $ajax_path = isset($ajax_settings['url']) ? $ajax_settings['url'] : url('system/ajax');
+    }
+    else {
+      $ajax_path = url($ajax_path);
     }
 
     // Submit the POST request.
@@ -2481,7 +2484,8 @@ class DrupalWebTestCase extends DrupalTestCase {
    * @param $path
    *   A path from the internal browser content.
    * @return
-   *   The $path with $base_url prepended, if necessary.
+   *   The $path with the internal browser's base URL or $base_url prepended, if
+   *   necessary.
    */
   protected function getAbsoluteUrl($path) {
     global $base_url, $base_path;
@@ -2490,6 +2494,20 @@ class DrupalWebTestCase extends DrupalTestCase {
     if (empty($parts['host'])) {
       // Ensure that we have a string (and no xpath object).
       $path = (string) $path;
+      // Return an absolute URL based on the internal browser's current URL if
+      // it is not using the internal: scheme.
+      $parts = parse_url($this->getUrl());
+      if ($parts['scheme'] != 'internal') {
+        $port = isset($parts['port']) ? ':' . $parts['port'] : '';
+        $url = $parts['scheme'] . '://' . $parts['host'] . $port;
+        if ($path[0] === '/') {
+          $url .= $path;
+        }
+        else {
+          $url .= preg_replace('@(.*/)([^/]*)@', '$1' . $path, $parts['path']);
+        }
+        return $url;
+      }
       // Strip $base_path, if existent.
       $length = strlen($base_path);
       if (substr($path, 0, $length) === $base_path) {