It took me a while to find out that Irssi: warning Could not verify SSL servers certificate: Irssi: warning Subject : /C=IE/L=Limerick/O=The University of Limerick Computer Society (Skynet)/CN=irc.skynet.ie/emailAddress=cypher@skynet. ie Irssi: warning Issuer : /O=Root CA/OU=http://www.cacert.org/CN=CA Cert Signing Authority/emailAddress=support@cacert.org Irssi: warning MD5 Fingerprint : AC:CE:26:F8:54:E1:E2:6D:1D:14:3E:9D:29:A3:E5:AB Irssi: critical g_io_error_get_from_g_error: assertion `err != NULL' failed means "the certificate has expired". It could be useful if irssi would be a little more talkative about what the actual problem is.