Adding approvals to work item in precondition (server side)

Hi, I'm trying to create a plugin which will automatically add an approval to a work item, if the plugin detects a certain status change.

Right now the code is experimental, and should add an approval to ALL status changes, but I can't get it to work. The entire operation runs fine, but no approvals are saved in the work item:

Object obj = operation.getOperationData();
		
SaveParameter data = (SaveParameter) obj;
	
// getting standard utilities
IWorkItemServer ws = getService(IWorkItemServer.class);			
IAuditableCommon wiCommon = ws.getAuditableCommon();
IRepositoryItemService rs = getService(IRepositoryItemService.class);
IAuditableServer as = getService(IAuditableServer.class);
		
		
		
// getting work item info
IWorkItem wi_old = (IWorkItem) data.getOldState();
IWorkflowInfo wfInfo_old = ws.getWorkflow(wi_old.getWorkItemType(), wi_old.getProjectArea(), monitor);
String workItemState_old = wfInfo_old.getStateName(wi_old.getState2());
		
IWorkItem wi = (IWorkItem) data.getNewState();
IWorkflowInfo wfInfo = ws.getWorkflow(wi.getWorkItemType(), wi.getProjectArea(), monitor);
String workItemState = wfInfo.getStateName(wi.getState2());
		
// if no state change occurred -> exit this advisor
if (workItemState.equals(workItemState_old))
{
	return;
}
		
wi_old = (IWorkItem) wi_old.getWorkingCopy();

IApprovals approvals= wi_old.getApprovals();
	
IApprovalDescriptor descriptor= approvals.createDescriptor(WorkItemApprovals.REVIEW_TYPE.getIdentifier(), "My approval");
IApproval approval= approvals.createApproval(descriptor, wi_old.getOwner());
approvals.add(approval);

ws.saveWorkItem2(wi_old, ws.resolveWorkItemReferences(wi_old, monitor), null);
		
IAdvisorInfo info = collector.createProblemInfo("WorkItem ("+wi.getId()+") - new state ["+workItemState+"]", "bla bla bla", this.getClass().getName());
collector.addInfo(info);
return;

Any ideas why this won't work?

Thanks a lot
/Morten.