Best practice "unknown datasource"

Hi, I do have some tables with table inheritance.

so I have table TblA and TblB

TblB inherits TblA.

On a form I use table TblA with a derived table TblB.

I added controls to the form using fields of Table TblB.

Best pratice check now shows me error "unknown datasource TblA_TblB" on the designlist node for such fields