Stardog post api for update Sparql queries return 400 Bad request error

I am trying to make a http post cal to stardog to insert data using sparql insert query
API: localhost:5820/platts-ontology/update
MEthod := post
headers := Content-Type: application/sparql-update
Payload : query=INSERT DATA { my triple to insert }

Error : 400 Bad Request

Can you please help me how to send update request using http api
I am following below documentation and dont see much help

I see the below error on error log
com.complexible.stardog.protocols.http.server.StardogUndertowErrorHandler:accept(68): Unexpected exception was handled by the server
java.lang.IllegalArgumentException: Query string cannot be empty

FYI, This works fine with python code and not from postman

import requests

url = 'http://localhost:5820/platts-ontology/update'
myobj = 'INSERT DATA {:S :P :O}'.encode()
myobj = 'INSERT DATA { <> a "asd" . }'

x =, data = myobj, headers = {"Content-Type": "application/sparql-update"})