diff --git a/html/upgrade.debian.8-9.html b/html/upgrade.debian.8-9.html
index 8f90aa8e..c8e4d3fa 100644
--- a/html/upgrade.debian.8-9.html
+++ b/html/upgrade.debian.8-9.html
@@ -30,7 +30,7 @@
 <p>Run commands:</p>
 <pre><code># Backup files
 cp /etc/postfix/main.cf /etc/postfix/main.cf.bak
-cp /etc/postfix/master.cf /etc/postfix/master.cf
+cp /etc/postfix/master.cf /etc/postfix/master.cf.bak
 
 # Update main.cf and master.cf
 postconf -e daemon_directory='/usr/lib/postfix/sbin'