diff -u b/core/modules/system/templates/html.html.twig b/core/modules/system/templates/html.html.twig
--- b/core/modules/system/templates/html.html.twig
+++ b/core/modules/system/templates/html.html.twig
@@ -31,7 +31,7 @@
{%
set body_classes = [
logged_in ? 'user-logged-in',
- is_front ? 'path-frontpage' : 'path-' ~ root_path|clean_class,
+ not root_path ? 'path-frontpage' : 'path-' ~ root_path|clean_class
]
%}