Why doesn't SSL_PROTOCOL and SSL_CIPHER logging in apache work?

Issue

• Why doesn't SSL_PROTOCOL and SSL_CIPHER logging in apache work?

Problematic configulation sample:

/etc/httpd/conf/httpd.conf
--------------------------
#Include conf.d/*.conf
Include conf.d/ssl.conf
Include conf.d/nss.conf


/etc/httpd/conf.d/ssl.conf
--------------------------
CustomLog logs/ssl_request_log \
          "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"

Problematic logging smaple:

/var/log/httpd/ssl_request_log
------------------------------
[15/Apr/2015:08:17:26 +0900] 192.168.122.1 - - "GET /test HTTP/1.1" 7

Expected logging sample:

[15/Apr/2015:08:37:57 +0900] 192.168.122.1 TLSv1 DHE-RSA-AES128-SHA "GET /test HTTP/1.1" 7