diff --git a/wp-admin/admin-header.php b/wp-admin/admin-header.php
index cbce31b59f..5322e2bb65 100644
--- a/wp-admin/admin-header.php
+++ b/wp-admin/admin-header.php
@@ -204,8 +204,9 @@ $admin_body_class .= ' no-customize-support no-svg';
* @param string $classes Space-separated list of CSS classes.
*/
$admin_body_classes = apply_filters( 'admin_body_class', '' );
+$admin_body_classes = ltrim( $admin_body_classes . ' ' . $admin_body_class );
?>
-<body class="wp-admin wp-core-ui no-js <?php echo $admin_body_classes . ' ' . $admin_body_class; ?>">
+<body class="wp-admin wp-core-ui no-js <?php echo $admin_body_classes; ?>">
<script type="text/javascript">
document.body.className = document.body.className.replace('no-js','js');
</script>
diff --git a/wp-admin/includes/template.php b/wp-admin/includes/template.php
index e7b3a2d6ec..16cf63d5d3 100644
--- a/wp-admin/includes/template.php
+++ b/wp-admin/includes/template.php
@@ -1788,6 +1788,7 @@ if ( is_rtl() ) {
<?php
/** This filter is documented in wp-admin/admin-header.php */
$admin_body_classes = apply_filters( 'admin_body_class', '' );
+$admin_body_classes = ltrim( $admin_body_classes . ' ' . $admin_body_class );
?>
<body
<?php
@@ -1798,7 +1799,7 @@ if ( isset( $GLOBALS['body_id'] ) ) {
echo ' id="' . $GLOBALS['body_id'] . '"';
}
?>
- class="wp-admin wp-core-ui no-js iframe <?php echo $admin_body_classes . ' ' . $admin_body_class; ?>">
+ class="wp-admin wp-core-ui no-js iframe <?php echo $admin_body_classes; ?>">
<script type="text/javascript">
(function(){
var c = document.body.className;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 6b6d0ded98..90aa71f4d1 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
*
* @global string $wp_version
*/
-$wp_version = '5.0-alpha-42973';
+$wp_version = '5.0-alpha-42974';
/**
* Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.