Disclosing Bind Version Number

I have two servers running Bind 9.3.1 and unfortunately bad guys can use the following to check the version number:

$dig @nameserver version.bind txt chaos
;; ANSWER SECTION:
VERSION.BIND. 0 CH TXT "9.3.1"

This is a security risk as hackers can check if the version in use contain buffer overflow vulnerabilities.

A simple work-around remedy is to insert the following in /var/named/chroot/etc/named.conf :

options {
version "Not disclosed";
}

Upon the same query, the answer returned is :
;; ANSWER SECTION:
VERSION.BIND. 0 CH TXT "Not disclosed"

I recommend system administrators to do the same for security sake.