diff --git a/Call/HttpPostJson.php b/Call/HttpPostJson.php
index 10ad36f..9c6071a 100644
--- a/Call/HttpPostJson.php
+++ b/Call/HttpPostJson.php
@@ -7,14 +7,14 @@
  *
  * @author Maurits van der Schee <m.vanderschee@leaseweb.com>
  */
-class HttpPostJson extends CurlCall implements ApiCallInterface
+class HttpPostJson extends HttpPost implements ApiCallInterface
 {
     /**
     * {@inheritdoc}
     */
     public function generateRequestData()
     {
-        $this->requestData = http_build_query($this->requestObject);
+        $this->requestData = json_encode($this->requestObject);
     }
 
     /**