Stunnel doesn't allow you to specify a location for the master CA Cert file. Thus whatever is determined at compile time is your only option. (The CA Cert file is used much like the 'trusted certificates' directory [-a] when -v3 is used) This patch adds an option '-A' that specifies the location of the CA Cert file. Usage: stunnel .... -A /path/to/ca_cert.pem To force it to use no ca_cert file, use '-A /dev/null' or an empty file.