HTTP to RFC

Hi Guys :

I got this error message in a HTTP to RFc scenario. I am basically using a BAPI.

Error: http-Status: 500 Internal Server Error

Payload:

<SAP:Error><SAP:Category>XIAdapterFramework</SAP:Category><SAP:Code>MESSAGE.GENERAL</SAP:Code><SAP:AdditionalText>com.sap.aii.af.ra.ms.api.DeliveryException: error while processing message to remote system:com.sap.aii.af.rfc.core.client.RfcClientException: failed to parse BAPI response due to: com.sap.aii.af.rfc.util.bapi.BapiException: Parameter with name RETURN not found.</SAP:AdditionalText></SAP:Error>

Can anyone tell me where the error is : XI side OR Bapi side and what could be done?

Thanks