Setting ReportSelection Formula

I am working on a report that needs to set its RecordSelectionFormula on the fly.  For some reason this selection formula tells me that a parenthesis is missing, and I just can't see where or why:

{vw_MiniPlanData.WeekYear}='201523' AND
({vw_MiniPlanData.InspectDate} < '2015-06-13' OR {vw_MiniPlanData.InspectDate} is null)

The purpose is to extract all the records where the WeekYear is 201523 and the InspectDate is less that 6/13/15 <OR> the InspectDate is null.  Any suggestions on what will fix this missing parenthesis?  I am running this under VisualStudio 2008 (VB.NET) and Crystal Reports 10.5.3500.0

Thanks!