diff --git a/wp-admin/includes/ms.php b/wp-admin/includes/ms.php
index b7e4c28631..2907d24735 100644
--- a/wp-admin/includes/ms.php
+++ b/wp-admin/includes/ms.php
@@ -185,6 +185,10 @@ function wpmu_delete_blog( $blog_id, $drop = false ) {
 function wpmu_delete_user( $id ) {
 	global $wpdb;
 
+	if ( ! is_numeric( $id ) ) {
+		return false;
+	}
+
 	$id = (int) $id;
 	$user = new WP_User( $id );
 
diff --git a/wp-admin/includes/user.php b/wp-admin/includes/user.php
index 3c2e26e186..5c12d3d265 100644
--- a/wp-admin/includes/user.php
+++ b/wp-admin/includes/user.php
@@ -273,6 +273,10 @@ function get_users_drafts( $user_id ) {
 function wp_delete_user( $id, $reassign = null ) {
 	global $wpdb;
 
+	if ( ! is_numeric( $id ) ) {
+		return false;
+	}
+
 	$id = (int) $id;
 	$user = new WP_User( $id );
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index f5e144c569..1a7b6acfdf 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-alpha-34033';
+$wp_version = '4.4-alpha-34034';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.