Proxy Bypass only specific IP

[TheBritishGeek]

I have tried 

        if ($remote_addr ~ "^(1.1.1.1|a:b:c:d::1:2)$")
        {
            proxy_cache_bypass $http_secret_header;
        }

But is does not pass testing

nginx: [emerg] "proxy_cache_bypass" directive is not allowed here

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,251124,251128#msg-251128