diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index e2f0d58..aa5ed49 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -1470,7 +1470,7 @@ public function randomStringValidate($string) {
 
     // Starting or ending with a space means that length might not be what is
     // expected.
-    if (preg_match('/^(\s.*)|(.*\s)$/', $string)) {
+    if (preg_match('/^\s|\s$/', $string)) {
       return FALSE;
     }