samba - Aug 2015 - Failed to open \$Extend\$Quota:$Q:$INDEX_ALLOCATION NT_STATUS_ACCESS_DENIED.

My environment is a Debian GNU/Linux with xfs filesystem and xfs quotas.

With samba-3.5.3 windows users got correct quota info from Explorer. Two
days ago I upgraded to samba-4.1.19, but now there is no longer quota info.

smbcquotas does not work.
$ sudo smbcquotas  -u user //domain/homes
Quotas are not enabled on this share.
Failed to open \$Extend\$Quota:$Q:$INDEX_ALLOCATION
NT_STATUS_ACCESS_DENIED.

What did I forget in order to allow samba4 to see xfs quotas?

$ testparm -v | grep quota
	get quota command 	set quota command 
thank you in advance,

Francesco