diff --git a/agaric/templates/container.html.twig b/agaric/templates/container.html.twig
new file mode 100644
index 0000000..ec1b750
--- /dev/null
+++ b/agaric/templates/container.html.twig
@@ -0,0 +1,3 @@
+{% extends "@stable/form/container.html.twig" %}
+
+{% set attributes = attributes.addClass("field") %}