apt-get 加 varnish 源后无法装上新源的最新程序？ why？

[baskice]

按照 https://www.varnish-cache.org/releases/install_debian.html 在腾讯云机器

apt-get install apt-transport-https
curl https://repo.varnish-cache.org/GPG-key.txt | apt-key add -
echo "deb https://repo.varnish-cache.org/debian/ jessie varnish-4.1"\
>> /etc/apt/sources.list.d/varnish-cache.list
apt-get update
apt-get install varnish

通常这样装完会获得 varnish4.1 。但是这个机器装完还是腾讯云里的旧版 4.0.2-1.
apt-cache policy varnish 显示：
varnish:
Installed: 4.0.2-1
Candidate: 4.0.2-1
Version table:
*** 4.0.2-1 0
500 http://mirrors.tencentyun.com/debian/ jessie/main i386 Packages
100 /var/lib/dpkg/status