diff -r e5dd3518be91 -r b4ebe523bb4e src/pyams_form/templates/form.pt
--- a/src/pyams_form/templates/form.pt	Wed Sep 20 12:13:36 2017 +0200
+++ b/src/pyams_form/templates/form.pt	Thu Sep 21 14:29:32 2017 +0200
@@ -55,7 +55,7 @@
 					<tal:loop repeat="group view.groups">
 						<fieldset tal:define="legend group.legend"
 								  tal:omit-tag="not:legend"
-								  tal:attributes="class 'bordered' if group.bordered else None">
+								  tal:attributes="class (group.fieldset_class or '') + (' bordered' if group.bordered else '')">
 							<tal:if condition="group.checkbox_switch">
 								<legend data-ams-checker-value="selected"
 										tal:condition="legend"