Non queried parameter - different behaviour SQL Server 2005, SQL Server 2008 R2

I have a report, which has a report parameter with the following prope开发者_如何学运维rties:

• hidden
• allow blank value
• non queried
• default value ( non-queried ) : dd/MM/yyyy

Report is started using the ReportExecution2005.asmx webservice.

• On SQL Server 2005, the web service runs the report without problems.
• On SQL Server 2008 R2, the web service returns an error:

This report requires a default or user-defined value for the report parameter 'datumformaat'. To run or subscribe to this report, you must provide a parameter value.

Can this be fixed somehow, to have the same behaviour as SQL Server 2005?

Parameter contained a null value, which was causing the error