diff -u b/core/modules/help/lib/Drupal/help/Tests/HelpTest.php b/core/modules/help/lib/Drupal/help/Tests/HelpTest.php
--- b/core/modules/help/lib/Drupal/help/Tests/HelpTest.php
+++ b/core/modules/help/lib/Drupal/help/Tests/HelpTest.php
@@ -67,7 +67,7 @@
     // Disable css aggregation so we can check if help.css exists.
     $system_performance = config('system.performance');
     $css_preprocess = $system_performance->get('css.preprocess');
-    $system_performance->set('css.preprocess', 0)->save();
+    $system_performance->set('css.preprocess', FALSE)->save();
     // Check for css on admin/help.
     $this->drupalLogin($this->adminUser);
     $this->drupalGet('admin/help');
diff -u b/core/profiles/standard/config/system.performance.yml b/core/profiles/standard/config/system.performance.yml
--- b/core/profiles/standard/config/system.performance.yml
+++ b/core/profiles/standard/config/system.performance.yml
@@ -2,3 +2,3 @@
-  preprocess: 1
+  preprocess: true
 js:
-  preprocess: 1
+  preprocess: true