Collection in Java object on MultiInstance

I have a Java object added as variable:

private Collection<BatchPayment> batchPayments = new ArrayList<BatchPayment>();

public Collection<BatchPayment> getBatchPayments() {
	return batchPayments;

public void setBatchPayments(Collection<BatchPayment> batchPayments) {
	this.batchPayments = batchPayments;

I’m trying to generate a MultiInstance task with the following configuration on the collection:


I’m getting this error:

13-Oct-2016 12:52:58.368 SEVERE [http-nio-8080-exec-13] org.camunda.commons.logging.BaseLogger.logError ENGINE-16004 Exception while closing command context: ENGINE-02025 Variable ‘state.batchPayments’ is not from type ‘Collection’.
org.camunda.bpm.engine.ProcessEngineException: ENGINE-02025 Variable ‘state.batchPayments’ is not from type ‘Collection’.
at org.camunda.bpm.engine.impl.bpmn.behavior.BpmnBehaviorLogger.invalidVariableTypeException(

If I create the collection in a direct variable, it does work:

	ArrayList<BatchPayment> lst = new ArrayList<BatchPayment>();
	lst.add(new BatchPayment());
	execution.setVariable("lst", lst);

Any ideas?

I’ve found out I had to use it like this in the collection:


Leave it as reference.