diff --git a/src/Phpforce/RestClient/Client.php b/src/Phpforce/RestClient/Client.php
index 2a0ce69..b1e3cf8 100644
--- a/src/Phpforce/RestClient/Client.php
+++ b/src/Phpforce/RestClient/Client.php
@@ -58,7 +58,7 @@ public function post($uri, array $arguments = array())
     {
         $request = $this->getClient()->post($uri);
         $request->setHeader('Authorization', 'Bearer ' . $this->getSessionId());
-        $request->getParams()->merge($arguments);
+        $request->setBody(json_encode($arguments), 'application/json');
 
         $response = $request->send();
 
@@ -99,4 +99,4 @@ protected function getSessionId()
     {
         return $this->getLoginResult()->getSessionId();
     }
-}
\ No newline at end of file
+}