DHCP + option 066

Hi everyone
I am trying that dhcp service sends the tftp server address to my voip phones with a option known for win-dhcp as option 066.

Man for dhcp-option says:

option tftp-server-name text;
This option is used to identify a TFTP server and, if supported by the client, should have the same effect as the server-name declaration. BOOTP clients are unlikely to support this option. Some DHCP clients will support it, and others actually require it.

Text must be enclosed in double quotes, but unfortunate option parameter is aswell used in vyos enclosed in quotes.

Using 172.16.1.50 (my tftp server) without qoutes,

dhcp-server {
disabled false
global-parameters “option tftp-server-name 172.16.1.50;”
shared-network-name CASA {
authoritative disable
subnet 172.16.1.0/24 {
default-router 172.16.1.1
dns-server 172.16.1.1
lease 86400
start 172.16.1.10 {
stop 172.16.1.100
}
}
}
}

I get dhcp not working

Jun 12 15:58:11 casa dhcpd: /opt/vyatta/etc/dhcpd.conf line 5: expecting string.
Jun 12 15:58:11 casa dhcpd: option tftp-server-name 172.
Jun 12 15:58:11 casa dhcpd: ^
Jun 12 15:58:11 casa dhcpd: Configuration file errors encountered – exiting

Trying alternatives

vyos@casa# delete service dhcp-server global-parameters

[edit]
vyos@casa# set service dhcp-server global-parameters “option tftp-server-name ‘172.16.1.50’;”

Cannot use the single quote (’) character in a value string
Value validation failed
Set failed

[edit]
vyos@casa# set service dhcp-server global-parameters ‘option tftp-server-name “172.16.1.50”;’

Cannot use the double quote (") character in a value string
Value validation failed
Set failed

[edit]
vyos@casa#

Thanks for your time

example:
set service dhcp-server shared-network-name CASA subnet 172.16.1.0/24 tftp-server-name 172.16.1.50