What's the gnu-netcat's '-z' equivalent option in nmap-ncat?

I check for a listening port on a service prior to running a script using this : until nc -z $HOST $PORT do echo "waiting for service to be available..." sleep 0.5 done exec "/my/script" It used to work with gnu-netcat, but now, I've upgraded the Linux distribution, and it uses nmap-ncat for the /usr/bin/nc command. I'd like to know an equivalent solution to use with nmap-ncat package.