Query workitem subscriptions from java API

When I try to query workitems by the IWorkItem.SUBSCRIPTIONS_PROPERTY using the java API, an exception is thrown (when I start iterating over the results):

com.ibm.team.repository.common.transport.ServiceMethodInvocationError: com.ibm.team.repository.common.query.QueryException: Unknown queryable field: internalSubscriptions

My code looks as follows:

IContributor subscriber = teamRepository.contributorManager().fetchContributorByUserId("myuid", null);		



if (subscriber == null) 

{

   throw new ItemNotFoundException("UserId not found");

}

		

IQueryableAttribute subscriptionAttribute = factory.findAttribute(projectArea, IWorkItem.SUBSCRIPTIONS_PROPERTY, auditableClient, null);

AttributeExpression subscriptionExpression = new AttributeExpression(subscriptionAttribute, AttributeOperation.CONTAINS, subscriber);

			    

Term term= new Term(Operator.AND);

term.add(projectAreaExpression);

term.add(subscriptionExpression);

		

IQueryResult<IResolvedResult<IWorkItem>> result = queryClient.getResolvedExpressionResults(projectArea, term, IWorkItem.FULL_PROFILE);



while (result.hasNext(null))

{

...

}

When I omit the subscriptionExpression from the query it works fine. Using this result set (which is then of course much bigger) I can get the subscriptions from each workitem in the result set and do the filtering afterward, but this seems sub-optimal.

Thanks,

Daan