[Samba] Samba 4.6.2 does not inherit setgid bit (anymore)

[Vincent]

Somewhere between Samba 4.2.10 and 4.6.2 (came with CentOS 7 updates) 
the setgid bit is not inherited anymore when making directories via my 
Samba service. Everything else is still fine. With ssh direct on the 
file system or sftp, i get all permissions and acls inherited nicely. 
Also with Samba all acls are still just fine, except that setgid bit is 
not inherited (s on the group executable bit becomes an x), so 
subsequent directories and files have the wrong group.

To test, i made a minimal share definition:

[global]
unix extensions = no
map archive = no
map hidden = no
map read only = no
map system = no
store dos attributes = yes

[test]
comment = Test
path = /var/test
writable = yes
inherit permissions = yes

The smb.conf reference says about "inherit permissions": New directories 
inherit the mode of the parent directory, including bits such as setgid.

Well, this is obviously not true anymore. The setgid bit is not even 
inherited in this minimal share definition. Do do i need to add other 
parameters to force setgid to inherit?

The setup is standalone and the file system is ext4 on a kvm guest.

Thanks for any information on this.

Kind regards, Vincent