diff -u b/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
--- b/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -185,8 +185,8 @@
  *     - description: (optional) A description of the module.
  *     - version: (optional) The version of the module.
  *     - links: (optional) Administration links provided by the module.
- *     - requires: (optional) A list of modules that the project requires.
- *     - required_by: (optional) A list of modules that require the project.
+ *     - #requires: (optional) A list of modules that the project requires.
+ *     - #required_by: (optional) A list of modules that require the project.
  */
 function template_preprocess_system_modules_details(&$variables) {
   $form = $variables['form'];
@@ -258,8 +258,8 @@
     $disabled_header = '';
     $disabled_reasons = '';
     // Add the modules requiring the module in question as a validation reason.
-    if (!empty($form['modules'][$module]['required_by'])) {
-      $form['modules'][$module]['#validation_reasons'][] = \Drupal::translation()->translate('Required by: @modules', array('@modules' => implode(', ',$form['modules'][$module]['required_by'])));
+    if (!empty($form['modules'][$module]['#required_by'])) {
+      $form['modules'][$module]['#validation_reasons'][] = \Drupal::translation()->translate('Required by: @modules', array('@modules' => implode(', ',$form['modules'][$module]['#required_by'])));
     }
     if (!empty($form['modules'][$module]['#validation_reasons'])) {
       $disabled_reasons = [