pipeline return value to parent pipeline

Hi

I want to pass return value from child pipeline to parent pipeline and followed the example mentioned in this guide.

Set Pipeline Return Value - Azure Data Factory & Azure Synapse | Microsoft Learn

Child pipeline 

Unfortunately I am getting error indicating the output property of pipelineReturnValue itself doesn't exist. 

The expression 'setProperty(json('{}'),'output',activity('Invoke pipeline1_copy1').output.pipelineReturnValue.child_return)' cannot be evaluated because property 'pipelineReturnValue' doesn't exist, available properties are 'id, itemId, jobType, invokeType, status, failureReason, rootActivityId, startTimeUtc, endTimeUtc, monitoringURL, pipelineRunId, ResponseHeaders, effectiveIntegrationRuntime, executionDuration, durationInQueue, billingReference'.

Strangely this works fine in legacy pipeline activity and not preview pipeline activity.