Server version: Apache/2.4.6

As per the documentation at [1], “In 2.4.5 and later, SSLProxyCheckPeerCN has been superseded by SSLProxyCheckPeerName, and its setting is only taken into account when SSLProxyCheckPeerName off is specified at the same time.”

So adding following entry did the trick:

SSLProxyCheckPeerName off

So my working config looks like…

    ProxyRequests Off

    SSLEngine On
    SSLProxyEngine On
    SSLProxyVerify none
    SSLProxyCheckPeerCN off
    SSLProxyCheckPeerName off

    SSLCertificateFile /x/x/keys/server.crt
    SSLCertificateKeyFile /x/x/keys/server.key

[1] http://httpd.apache.org/docs/2.4/mod/mod_ssl.html