This seems to work with the lastest stable release (1.5): $ /usr/lib/nagios/plugins/check_http -I 127.0.0.1 -p 8888 -H 'domain.org:80' -v | head -4 GET / HTTP/1.1 User-Agent: check_http/v1.5 (nagios-plugins 1.5) Connection: close Host: domain.org:80
So I'm closing this issue. -- Reply to this email on GitHub: https://github.com/monitoring-plugins/monitoring-plugins/issues/1026#issuecomment-46850782