diff --git a/wp-admin/includes/ajax-actions.php b/wp-admin/includes/ajax-actions.php
index e125014dd7..be8337495a 100644
--- a/wp-admin/includes/ajax-actions.php
+++ b/wp-admin/includes/ajax-actions.php
@@ -3605,7 +3605,7 @@ function wp_ajax_crop_image() {
 
 	switch ( $context ) {
 		case 'site-icon':
-			require_once ABSPATH . '/wp-admin/includes/class-wp-site-icon.php';
+			require_once ABSPATH . 'wp-admin/includes/class-wp-site-icon.php';
 			$wp_site_icon = new WP_Site_Icon();
 
 			// Skip creating a new attachment if the attachment is a Site Icon.
diff --git a/wp-includes/class-wp-customize-manager.php b/wp-includes/class-wp-customize-manager.php
index 81be17b79d..587c02d43d 100644
--- a/wp-includes/class-wp-customize-manager.php
+++ b/wp-includes/class-wp-customize-manager.php
@@ -402,7 +402,7 @@ final class WP_Customize_Manager {
 
 		// Add theme update notices.
 		if ( current_user_can( 'install_themes' ) || current_user_can( 'update_themes' ) ) {
-			require_once ABSPATH . '/wp-admin/includes/update.php';
+			require_once ABSPATH . 'wp-admin/includes/update.php';
 			add_action( 'customize_controls_print_footer_scripts', 'wp_print_admin_notice_templates' );
 		}
 	}
diff --git a/wp-includes/class-wp-customize-widgets.php b/wp-includes/class-wp-customize-widgets.php
index d45f7c5207..eaa29c228b 100644
--- a/wp-includes/class-wp-customize-widgets.php
+++ b/wp-includes/class-wp-customize-widgets.php
@@ -949,7 +949,7 @@ final class WP_Customize_Widgets {
 		}
 
 		global $wp_registered_widgets, $wp_registered_widget_controls;
-		require_once ABSPATH . '/wp-admin/includes/widgets.php'; // for next_widget_id_number()
+		require_once ABSPATH . 'wp-admin/includes/widgets.php'; // for next_widget_id_number()
 
 		$sort = $wp_registered_widgets;
 		usort( $sort, array( $this, '_sort_name_callback' ) );
diff --git a/wp-includes/customize/class-wp-widget-form-customize-control.php b/wp-includes/customize/class-wp-widget-form-customize-control.php
index 260b417f46..cfab188606 100644
--- a/wp-includes/customize/class-wp-widget-form-customize-control.php
+++ b/wp-includes/customize/class-wp-widget-form-customize-control.php
@@ -96,7 +96,7 @@ class WP_Widget_Form_Customize_Control extends WP_Customize_Control {
 		}
 
 		// Get the widget_control and widget_content.
-		require_once ABSPATH . '/wp-admin/includes/widgets.php';
+		require_once ABSPATH . 'wp-admin/includes/widgets.php';
 
 		$widget = $wp_registered_widgets[ $this->widget_id ];
 		if ( ! isset( $widget['params'][0] ) ) {
diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
index bc0a179f7f..0e3489c183 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php
@@ -1614,7 +1614,7 @@ class WP_REST_Posts_Controller extends WP_REST_Controller {
 		if ( is_post_type_viewable( $post_type_obj ) && $post_type_obj->public ) {
 
 			if ( ! function_exists( 'get_sample_permalink' ) ) {
-				require_once ABSPATH . '/wp-admin/includes/post.php';
+				require_once ABSPATH . 'wp-admin/includes/post.php';
 			}
 
 			$sample_permalink = get_sample_permalink( $post->ID, $post->post_title, '' );
diff --git a/wp-includes/update.php b/wp-includes/update.php
index c815d157aa..824575099b 100644
--- a/wp-includes/update.php
+++ b/wp-includes/update.php
@@ -595,8 +595,8 @@ function wp_update_themes( $extra_stats = array() ) {
  * @since 3.7.0
  */
 function wp_maybe_auto_update() {
-	include_once( ABSPATH . '/wp-admin/includes/admin.php' );
-	include_once( ABSPATH . '/wp-admin/includes/class-wp-upgrader.php' );
+	include_once( ABSPATH . 'wp-admin/includes/admin.php' );
+	include_once( ABSPATH . 'wp-admin/includes/class-wp-upgrader.php' );
 
 	$upgrader = new WP_Automatic_Updater;
 	$upgrader->run();