diff --git a/modules/simpletest/drupal_web_test_case.php b/modules/simpletest/drupal_web_test_case.php
index 50f3109..26bf2f2 100644
--- a/modules/simpletest/drupal_web_test_case.php
+++ b/modules/simpletest/drupal_web_test_case.php
@@ -2765,7 +2765,7 @@ protected function getAbsoluteUrl($path) {
         $path = substr($path, $length);
       }
       // Ensure that we have an absolute path.
-      if ($path[0] !== '/') {
+      if (empty($path) || $path[0] !== '/') {
         $path = '/' . $path;
       }
       // Finally, prepend the $base_url.