diff --git a/wp-includes/user.php b/wp-includes/user.php
index 7bdc37cc76..56e6d082a5 100644
--- a/wp-includes/user.php
+++ b/wp-includes/user.php
@@ -1452,6 +1452,8 @@ function wp_update_user($userdata) {
 
 	// First, get all of the original fields
 	$user_obj = get_userdata( $ID );
+	if ( ! $user_obj )
+		return new WP_Error( 'invalid_user_id', __( 'Invalid user ID.' ) );
 
 	$user = $user_obj->to_array();