2.7.4 explicitly calls for use of a deprecated back level of TLS. On Debian stretch, after ./configure --with-openssl, make produces the following warning: upsclient.c: In function 'upscli_init': upsclient.c:322:2: warning: 'TLSv1_client_method' is deprecated [-Wdeprecated-declarations] ssl_method = TLSv1_client_method(); ^~~~~~~~~~ A similar warning about TLSv1_server_method appears at netssl.c:392. I understand from https://users-cs.au.dk/sortie/sortix/release/nightly/man/man3/TLSv1_server_method.3.html that version flexible TLS_server_method() is now preferred. See Issue 575 for more detail. https://github.com/networkupstools/nut/issues/575 Roger