Hello.
It may depends on development model - Portal engine or ASPX templates. The thing is that this property cannot be used for ASPX templates. The ASPX model doesn't have inheritance possibilities. The problem is that this property is available without any information (comment, exception or something like that, that it cannot be used) so it may lead to some confusion then. To be honest with you I though it should work on ASPX templates too, however I was ensured by our developer that it does not.
If it worked in previous version, maybe there were some special circumstances or so, however it was not and it is not designed or expected functionality.
Luckily, there is a workaround for ASPX templates as well. Please find it
here.Best Regards,
Radek Macalik