diff --git a/core/tests/Drupal/Tests/Component/Utility/RandomTest.php b/core/tests/Drupal/Tests/Component/Utility/RandomTest.php
index b9c7a4e..a3e7b8c 100644
--- a/core/tests/Drupal/Tests/Component/Utility/RandomTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/RandomTest.php
@@ -169,7 +169,9 @@ public function testRandomStringValidator() {
    *   TRUE if the random string is valid, FALSE if not.
    */
   public function _RandomStringValidate($string) {
-    if (empty($this->firstStringGenerated)) {
+    // Return FALSE for the first generated string and any string that is the
+    // same, as the test expects a different string to be returned.
+    if (empty($this->firstStringGenerated) || $string == $this->firstStringGenerated) {
       $this->firstStringGenerated = $string;
       return FALSE;
     }