diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php
index 1b54825..8be1055 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityUnitTest.php
@@ -45,7 +45,7 @@ public function testStorageControllerMethods() {
     $this->assertIdentical($controller::getIDFromConfigName($config_name, $info['config_prefix']), $expected_id);
 
     // Create three entities, two with the same style.
-    $style = $this->randomName();
+    $style = $this->randomName(8);
     for ($i = 0; $i < 2; $i++) {
       $entity = $controller->create(array(
         'id' => $this->randomName(),
@@ -57,7 +57,8 @@ public function testStorageControllerMethods() {
     $entity = $controller->create(array(
       'id' => $this->randomName(),
       'label' => $this->randomString(),
-      'style' => $this->randomName(),
+      // Use a different length for the entity to ensure uniqueness.
+      'style' => $this->randomName(9),
     ));
     $entity->save();