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
@@ -265,7 +265,7 @@
     }
     $title = [
       '#type' => 'inline_template',
-      '#template' => '<span class="text">{{ module_description }}</span>',
+      '#template' => '<span class="text module-description">{{ module_description }}</span>',
       '#context' => ['module_description' => $module['description']],
     ];
     $details = array(