Use only TLSv1.2 (no replies)

Running RHEL 7.4 and MySQL Cluster 7.6.4 (5.7.20) installed via yum.
I can connect over SSL, but I get TLSv1.1.
I would prefer TLSv1.2.
Adding tls_version=TLSv1.2 to /etc/my.cnf causes an error:

Failed to set up SSL because of the following SSL library error: TLS version is invalid

I believe I am using OpenSSL (not yaSSL).
show variables like '%ssl%' returns:
have_openssl YES
have_ssl YES

Using GlobalSign certificate.
ssl_ca = Globalsign root certificate (without the intermediate)
ssl_cert = the cert they gave me
ssl_key = key openssl created (then converted to RSA)
All owned by the mysql user...

Brian