diff --git a/core/misc/drupal.base.css b/core/misc/drupal.base.css
index 980ff81..9d52f2c 100644
--- a/core/misc/drupal.base.css
+++ b/core/misc/drupal.base.css
@@ -16,7 +16,9 @@ figcaption,
 figure,
 footer,
 header,
+hgroup,
 main,
+menu,
 nav,
 section,
 summary {
@@ -39,6 +41,9 @@ label {
   display: block;
   font-weight: bold;
 }
+button {
+  font-size: 1em;
+}
 input {
   /* Keep form elements from overflowing their containers. */
   max-width: 100%;
diff --git a/core/modules/system/css/system.theme.css b/core/modules/system/css/system.theme.css
index 126eb9f..536cd93 100644
--- a/core/modules/system/css/system.theme.css
+++ b/core/modules/system/css/system.theme.css
@@ -355,9 +355,6 @@ ul.tabs {
 /**
  * Styles for link buttons and action links.
  */
-button {
-  font-size: 1em;
-}
 .action-links {
   list-style: none;
   padding: 0;