BIND forward to Windows DNS

Hello,

We have a BIND server authoritative for zone "company.com". After som
years we implemented Microsoft AD with its own DNS server in its own
zone "ad.company.com". The Microsoft server is authoritative for
"ad.company.com"

Now we want clients that have the BIND server as their configured DNS
server to be able to resolve hosts in the "ad.company.com" zone. I
thought this was simply done by creating a forward zone on the BIND
server pointing to the Windows DNS server alternatively using the
"forwarders" option. This however does not seem to work.

Is there something I am missing here?

Kind regards,
Rutger Blom