[stunnel-users] Connection failed: no suitable signature algorithm

I'm trying to understand this error: SSL_accept: ssl/t1_lib.c:2827: error:14201076:SSL routines:tls_choose_sigalg:no suitable signature algorithm How can I fix that? Is it because of the openssl version? I'm using Stunnel 5.71 on both sides. The server-side stunnel is built from source.