diff --git a/core/modules/system/css/system.admin.css b/core/modules/system/css/system.admin.css
index add899d..7b5fe1f 100644
--- a/core/modules/system/css/system.admin.css
+++ b/core/modules/system/css/system.admin.css
@@ -48,12 +48,7 @@
  * Administration blocks.
  */
 .admin-panel {
-  margin: 0;
-  padding: 5px 5px 15px 5px;
-}
-.admin-panel .description {
-  margin: 0 0 3px;
-  padding: 2px 0 3px 0;
+  padding: 5px 5px 15px;
 }
 
 /**
diff --git a/core/modules/system/templates/admin-block.html.twig b/core/modules/system/templates/admin-block.html.twig
index 20aa000..5cd4de1 100644
--- a/core/modules/system/templates/admin-block.html.twig
+++ b/core/modules/system/templates/admin-block.html.twig
@@ -16,11 +16,11 @@
 #}
 <div class="admin-panel">
   {% if block.title %}
-    <h3>{{ block.title }}</h3>
+    <h3 class="admin-panel__title">{{ block.title }}</h3>
   {% endif %}
   {% if block.content %}
-    <div class="body">{{ block.content }}</div>
+    <div class="admin-panel__body">{{ block.content }}</div>
   {% elseif block.description %}
-    <div class="description">{{ block.description }}</div>
+    <div class="admin-panel__description">{{ block.description }}</div>
   {% endif %}
 </div>
diff --git a/core/themes/bartik/css/components/admin.css b/core/themes/bartik/css/components/admin.css
index 1661946..8761241 100644
--- a/core/themes/bartik/css/components/admin.css
+++ b/core/themes/bartik/css/components/admin.css
@@ -28,22 +28,19 @@
 }
 
 /* Configuration. */
-div.admin-panel {
+.admin-panel {
   background: #fbfbfb;
   border: 1px solid #ccc;
   margin: 10px 0;
   padding: 0 5px 5px;
 }
-div.admin-panel h3 {
+.admin-panel__title {
   margin: 16px 7px;
 }
-div.admin-panel dt {
+.admin-list dt {
   border-top: 1px solid #ccc;
   padding: 7px 0 0;
 }
-div.admin-panel dd {
+.admin-list dd {
   margin: 0 0 10px;
 }
-div.admin-panel .description {
-  margin: 0 0 14px 7px;
-}
diff --git a/core/themes/seven/css/components/admin-list.css b/core/themes/seven/css/components/admin-list.css
index 5d0b63d..2014b37 100644
--- a/core/themes/seven/css/components/admin-list.css
+++ b/core/themes/seven/css/components/admin-list.css
@@ -44,3 +44,7 @@ ul.admin-list {
 .admin-list li a:active .label {
   text-decoration: underline;
 }
+.admin-list .description {
+  margin: 0 0 3px;
+  padding: 2px 0 3px 0;
+}
diff --git a/core/themes/seven/css/components/admin-panel.css b/core/themes/seven/css/components/admin-panel.css
index ad27d3b..5cab4f0 100644
--- a/core/themes/seven/css/components/admin-panel.css
+++ b/core/themes/seven/css/components/admin-panel.css
@@ -1,18 +1,13 @@
 /**
  * Admin panel.
  */
-div.admin-panel,
-div.admin-panel .body {
-  padding: 0;
-  clear: left;
-}
-div.admin-panel {
-  margin: 0 0 20px;
+.admin-panel {
+  margin-bottom: 20px;
   padding: 9px;
   background: #f8f8f8;
   border: 1px solid #ccc;
 }
-div.admin-panel h3 {
+.admin-panel__title {
   font-size: 0.923em;
   text-transform: uppercase;
   margin: 0;