"Overriding Members" does not work correct in VB

I have found, that the "overriding members" function does not work for optional parameters in VB.

Sample:

Friend MustOverride Function NewIndex(ByRef pWertTyp As Integer, _
ByRef pZeiteinheit As Integer, _
ByRef pDatum As Date, _
ByRef pWert As Double, _
Optional ByRef pNotForDatabase As Integer = 0, _
Optional ByRef pObjZoId As Integer = -3) As Integer

is implemented as

Friend Overrides Function NewIndex(ByRef pWertTyp As Integer, _
ByRef pZeiteinheit As Integer, _
ByRef pDatum As Date, _
ByRef pWert As Double, _
ByRef pNotForDatabase As Integer, _
ByRef pObjZoId As Integer) As Integer

Regards
Klaaus