How to set PowerDNS Server with option any-to-tcp

I install PowerDNS with MySql backend from here.I would like to set  
any-to-tcp=yes for PowerDNS Server. I tried to configure  
/etc/powerdns/pdns.conf file and add a line "any-to-tcp=yes". This  
option should reject UDP request from client and force to use tcp. But  
when i run dig @127.0.0.1 it doesn't set the truncated bit in  
response, so it doesn't work.

How to set correctly any-to-tcp option ?