diff -u b/core/modules/system/css/system.theme.css b/core/modules/system/css/system.theme.css
--- b/core/modules/system/css/system.theme.css
+++ b/core/modules/system/css/system.theme.css
@@ -433,11 +433,11 @@
   margin: 1em 0 0.5em;
   padding: 0;
 }
-.tabs > li {
+.tabs__tab {
   display: inline-block;
   margin-right: 0.3em; /* LTR */
 }
-[dir="rtl"] .tabs > li {
+[dir="rtl"] .tabs__tab {
   margin-left: 0.3em;
   margin-right: 0;
 }
diff -u b/core/themes/bartik/css/colors.css b/core/themes/bartik/css/colors.css
--- b/core/themes/bartik/css/colors.css
+++ b/core/themes/bartik/css/colors.css
@@ -12,10 +12,10 @@
 .region-primary-menu .menu li .active-trail a {
   background: #ffffff;
 }
-nav .tabs--primary li a.active {
+.tabs--primary a.active {
   background-color: #ffffff;
 }
-nav .tabs--primary li.active a {
+.tabs--primary li.active a {
   background-color: #ffffff;
   border-bottom-color: #ffffff;
 }