Passing JSON object to untyped REST service in SOA BPEL

I am trying to pass a JSON object to an untyped rest service by assigning a JSON payload to the request variable.

First of all assigning a JSON string '{"init":1,"store_id":1002,"last_stock_count_id":545}' to a JSON object variable 'jsonObject'

Then passing this variable to rest webservice invoke.

While testing the service, its breaking in the invoke with below error:

<messages><input><jsonObject><json>{"store_id": 1002,"init": 1,"count_id": 545}</json></jsonObject></input><fault><bpelFault><faultType>0</faultType><remoteFault xmlns="http://schemas.oracle.com/bpel/extension"><part name="summary"><summary>oracle.fabric.common.FabricInvocationException: Rest reference payload type mismatchdefault/SIOCSClearUnavailableSOH!1.0/RDSUnavailableSOH</summary></part><part name="code"><code>null</code></part><part name="detail"><detail>Missing comma in object literal</detail></part></remoteFault></bpelFault></fault><faultType><message>0</message></faultType></messages>