> Works for me: heh. of COURSE it does! sanity check here, openssl ciphers -stdname -s -V 'TTLS13-CHACHA20-POLY1305-SHA256:TLS13-AES-128-GCM-SHA256:TLS13-AES-256-GCM-SHA384' Error in cipher list 140042399306176:error:1410D0B9:SSL routines:SSL_CTX_set_cipher_list:no cipher match:ssl/ssl_lib.c:2549: > Different OpenSSL release? yes openssl version OpenSSL 1.1.1c 28 May 2019 > Difference in build configuration? yes openssl version -f -p platform: linux-x86_64 compiler: /usr/bin/gcc-9 -fPIC -pthread -m64 -Wa,--noexecstack -O3 -Wall -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fmessage-length=0 -grecord-gcc-switches -march=native -mtune=native -fno-common -DOPENSSL_USE_NODELETE -DL_ENDIAN -DOPENSSL_PIC -DOPENSSL_CPUID_OBJ -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DKECCAK1600_ASM -DRC4_ASM -DMD5_ASM -DAES_ASM -DVPAES_ASM -DBSAES_ASM -DGHASH_ASM -DECP_NISTZ256_ASM -DX25519_ASM -DPOLY1305_ASM -DNDEBUG -D_GNU_SOURCE -DOPENSSL_NO_BUF_FREELISTS -DOPENSSL_NO_HEARTBEATS -DPURIFY -DSSL_FORBID_ENULL -DTERMIO -O3 -Wall -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fmessage-length=0 -grecord-gcc-switches -march=native -mtune=native -D_FORTIFY_SOURCE=2 which is quite different than yours. the config which I start with ./config -v \ --prefix=/usr/local/openssl11 \ --openssldir=/usr/local/openssl11 \ --libdir=lib64 \ -D_GNU_SOURCE \ -DOPENSSL_NO_BUF_FREELISTS \ -DOPENSSL_NO_HEARTBEATS \ -DPURIFY \ -DSSL_FORBID_ENULL \ -DTERMIO \ -Wa,--noexecstack \ -Wl,-z,relro,-z,now \ -Wall \ -Wl,-rpath=/usr/local/openssl11 \ -fno-common \ threads shared \ no-comp no-zlib no-zlib-dynaemic \ enable-ec_nistp_64_gcc_128 \ no-sctp \ no-idea \ no-mdc2 \ no-rc2 \ no-rc5 \ no-ssl3 \ no-weak-ssl-ciphers \ no-nextprotoneg That, too, is 'old' (been in use for a loooong time ...), and probably can benefit from some clean-up. As to what of that^ is causing my fail ... ? not immediately clear what the culprit is. Before I start decomposing the config difference, anything obvious leap out at you? > Configuration file difference? which config file are you referring to?