SmartObject Yes/No Type

I've got a SmartObject with a property that has a Yes/No type.  The underlying service object is the Dynamic SQL Service and the datatype of the field is bit.  When I access the field in my ASP.NET page, the SmartObject is returning a value of "false" even though the sql field is null.  Can anyone tell me if this is expected behavior of the SmartObject?  I've looked the the SQL Service object code, but I don't see anything obvious there.