diff --git a/wp-admin/admin-header.php b/wp-admin/admin-header.php
index cbce31b..7ec7dac 100644
--- a/wp-admin/admin-header.php
+++ b/wp-admin/admin-header.php
@@ -205,7 +205,7 @@ $admin_body_class .= ' no-customize-support no-svg';
  */
 $admin_body_classes = apply_filters( '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 ltrim( $admin_body_classes . ' ' . $admin_body_class ); ?>">
 <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 e7b3a2d..d2884f6 100644
--- a/wp-admin/includes/template.php
+++ b/wp-admin/includes/template.php
@@ -1798,7 +1798,7 @@ 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 ltrim( $admin_body_classes . ' ' . $admin_body_class ); ?>">
 <script type="text/javascript">
 (function(){
 var c = document.body.className;
@@ -2165,7 +2165,7 @@ function _wp_admin_html_begin() {
 ?>
 <!DOCTYPE html>
 <!--[if IE 8]>
-<html xmlns="http://www.w3.org/1999/xhtml" class="ie8 <?php echo $admin_html_class; ?>" 
+<html xmlns="http://www.w3.org/1999/xhtml" class="ie8 <?php echo $admin_html_class; ?>"
 																	<?php
 																	/**
 																	 * Fires inside the HTML tag in the admin header.
@@ -2177,7 +2177,7 @@ function _wp_admin_html_begin() {
 	<?php language_attributes(); ?>>
 <![endif]-->
 <!--[if !(IE 8) ]><!-->
-<html xmlns="http://www.w3.org/1999/xhtml" class="<?php echo $admin_html_class; ?>" 
+<html xmlns="http://www.w3.org/1999/xhtml" class="<?php echo $admin_html_class; ?>"
 																<?php
 																/** This action is documented in wp-admin/includes/template.php */
 																do_action( 'admin_xml_ns' );
