diff -u b/core/modules/system/lib/Drupal/system/Tests/Form/ModulesListFormWebTest.php b/core/modules/system/lib/Drupal/system/Tests/Form/ModulesListFormWebTest.php
--- b/core/modules/system/lib/Drupal/system/Tests/Form/ModulesListFormWebTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Form/ModulesListFormWebTest.php
@@ -35,7 +35,7 @@
    */
   public function setUp() {
     parent::setUp();
-    \Drupal::state()->get('system_test.module_hidden', FALSE);
+    \Drupal::state()->set('system_test.module_hidden', FALSE);
   }
 
   /**
diff -u b/core/modules/system/tests/modules/system_test/system_test.module b/core/modules/system/tests/modules/system_test/system_test.module
--- b/core/modules/system/tests/modules/system_test/system_test.module
+++ b/core/modules/system/tests/modules/system_test/system_test.module
@@ -43,7 +43,7 @@
   static $test;
   if (($dependencies = \Drupal::state()->get('system_test.dependencies')) || $test) {
     if ($file->name == 'module_test') {
-      $info['hidden'] =  \Drupal::state()->get('system_test.module_hidden', TRUE);
+      $info['hidden'] = FALSE;
       $info['dependencies'][] = array_shift($dependencies);
       \Drupal::state()->set('system_test.dependencies', $dependencies);
       $test = TRUE;
@@ -70,7 +70,7 @@
     $info['hidden'] = FALSE;
   }
   if ($file->name == 'system_test') {
-    $info['hidden'] = FALSE;
+    $info['hidden'] = \Drupal::state()->get('system_test.module_hidden', TRUE);
   }
 }