SSRS 2016 Subscription - Leave NULL option reverts to default

Hi All, We have recently migrated our reports from 2008 R2 to Reporting Services 2016 Have noticed an issue with a report that has a date parameter The DateTo parameter has a default of today's date with an option to tick the Null box The report works fine and returns the correct data based upon the date parameter (including when NULL) However the problem is when creating a subscription. In the subscription I choose the 'Leave Null' option for the DateTo parameter and Create the subscription successfully. But when I edit the subscription the DateTo parameter is set to 'Use Default Value' I have tested this behaviour against our old 2008 R2 RS and there is not a problem. Does anyone know of a fix for this for RS 2016 Thanks Anthony