diff -u b/core/themes/seven/css/components/form.css b/core/themes/seven/css/components/form.css
--- b/core/themes/seven/css/components/form.css
+++ b/core/themes/seven/css/components/form.css
@@ -5,15 +5,14 @@
   margin: 0;
   padding: 0;
 }
-fieldset {
+fieldset:not(.fieldgroup) {
   background-color: #fcfcfa;
   border-radius: 2px;
   margin: 1em 0;
   padding-top: 30px;
   position: relative;
 }
-fieldset legend{
-  font-family: 'Source Sans Pro','Lucida Grande', sans-serif;
+fieldset:not(.fieldgroup) legend{
   font-size: 1em;
   font-weight: bold;
   letter-spacing: 0.08em;