Find out Nmap version you are running on your machine with the -V option.

nmap -V

result:

Nmap version 6.40 ( http://nmap.org )
Platform: x86_64-pc-linux-gnu
Compiled with: liblua-5.2.3 openssl-1.0.1f libpcre-8.31 libpcap-1.5.3 nmap-libdnet-1.12 ipv6
Compiled without:
Available nsock engines: epoll poll select