halp

de error:
Catchable fatal error: Object of class mysqli_result could not be converted to string in F:\school\root\GIP\webpaginas\bestelBon.php on line 13

de code (session word geopened in header):
<?php
include("header.php");
include("nav1.html");
$servername ="localhost";
$username = "root";
$password = "usbw";
$dbname = "GIP";

$connect1 = new mysqli($servername, $username, $password, $dbname);
if(isset($_POST["btnBestel"])){
	$sql = "SELECT `Klant_ID` FROM klanten WHERE Klant_Login = \"".$_SESSION['login']."\"";
	$klantID = $connect1->query($sql);
	echo $klantID;
	$sql = "INSERT INTO `bestelling` VALUES(NULL, ".$klantID.", ".$_SESSION['totaal'].")";
	echo $sql;
	$qresult = $connect1->query($sql);
}
?>