Calling Copy action in custom action -Service Request

Dear Experts,

We have created a custom action copy(not mass enabled) and added it to SR TI screen as shown below.

On click of this button, we want to call standard copy action of service request using below code.

ServiceRequest.Copy(this);// this code is written in custom copy action.

But we get below dump

Source type \INTERFACE=IF_SERVICE_REQUEST\TYPE=TY_ROOT is not compatible, for the purposes of assignment, with target type \CLASS-POOL=BO_SERVICE_REQUEST\CLASS=ROOT\TYPE=TY_STRUCTURE

Any pointers ?

Regards

Rituraj