Отключить IPv6 в nginx proxy_pass

У моего сервера нет адресов IPv6.

Однако, когда я использую Nginx proxy_pass для восходящего потока с IPv4 и IPv6, иногда он пытается отправлять исходящие запросы с использованием IPv6:

2013/07/30 00:25:06 [error] 1930#0: *1482670 connect() to [AAAA:BBBB:C:DDD:E:F:GGG:HHH]:443 failed (101: Network is unreachable) while connecting to upstream, client: AA.BB.CC.DD, server: example.com, request: "GET /download/file HTTP/1.0", upstream: "https://[AAAA:BBBB:C:DDD:E:F:GGG:HHH]:443/download/file", host: "example.com"

Как отключить IPv6 для исходящих запросов в proxy_pass?

nginx.conf:

upstream download {
  server download.example.com:443;
  keepalive 8;
}

location /download {
  proxy_set_header      X-Forwarded-For  $proxy_add_x_forwarded_for;
  proxy_set_header      Connection "";
  proxy_ignore_headers  X-Accel-Redirect;
  proxy_http_version    1.1;
  resolver              8.8.8.8;
  resolver_timeout      5s;
  proxy_pass            https://download;
}

nginx -V:

nginx version: nginx/1.4.2
built by gcc 4.7.2 (Debian 4.7.2-5)
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/var/cache/nginx/client_temp --http-proxy-temp-path=/var/cache/nginx/proxy_temp --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp --http-scgi-temp-path=/var/cache/nginx/scgi_temp --user=nginx --group=nginx --with-http_ssl_module --with-http_realip_module --with-http_addition_module --with-http_sub_module --with-http_dav_module --with-http_flv_module --with-http_mp4_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_random_index_module --with-http_secure_link_module --with-http_stub_status_module --with-mail --with-mail_ssl_module --with-file-aio --with-http_spdy_module --with-cc-opt='-g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2' --with-ld-opt=-Wl,-z,relro --with-ipv6

ОС: Debian Wheezy

Linux 3.2.0-4-amd64 #1 SMP Debian 3.2.46-1 x86_64 GNU/Linux

ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 6c:62:6d:7a:ea:af brd ff:ff:ff:ff:ff:ff
    inet XXX.XXX.XXX.XXX/27 brd XXX.XXX.XXX.XXX scope global eth0