diff --git modules/simpletest/tests/form.test modules/simpletest/tests/form.test
index c515894..7e83f10 100644
--- modules/simpletest/tests/form.test
+++ modules/simpletest/tests/form.test
@@ -865,7 +865,7 @@ class FormsRebuildTestCase extends DrupalWebTestCase {
 
     // Ensure that the form contains two items in the multi-valued field, so we
     // know we're testing a form that was correctly retrieved from cache.
-    $this->assert(count($this->xpath('//form[@id="page-node-form"]//div[contains(@class, "field-name-field-ajax-test")]//input[@type="text"]')) == 2, t('Form retained its state from cache.'));
+    $this->assert(count($this->xpath('//form[contains(@id, "page-node-form")]//div[contains(@class, "form-item-field-ajax-test")]//input[@type="text"]')) == 2, t('Form retained its state from cache.'));
 
     // Ensure that the form's action is correct.
     $forms = $this->xpath('//form[contains(@class, "node-page-form")]');