diff --git a/buildserver/provision-apt-get-install b/buildserver/provision-apt-get-install
index 7051e32e..0b02d4c5 100644
--- a/buildserver/provision-apt-get-install
+++ b/buildserver/provision-apt-get-install
@@ -20,13 +20,14 @@ if echo $debian_mirror | grep '^https' 2>&1 > /dev/null; then
     apt-get -y install apt-transport-https ca-certificates
 fi
 
-sed -Ei "s,^deb [a-z]+://\S+,deb ${debian_mirror}," /etc/apt/sources.list
-
-if grep --quiet stretch /etc/apt/sources.list; then
-    echo "deb $debian_mirror stretch-backports main" > /etc/apt/sources.list.d/stretch-backports.list
-    echo "deb $debian_mirror testing main" > /etc/apt/sources.list.d/testing.list
-    printf "Package: *\nPin: release o=Debian,a=testing\nPin-Priority: -300\n" > /etc/apt/preferences.d/debian-testing
-fi
+cat << EOF > /etc/apt/sources.list
+deb ${debian_mirror} stretch main
+deb http://security.debian.org/debian-security stretch/updates main
+deb ${debian_mirror} stretch-updates main
+EOF
+echo "deb ${debian_mirror} stretch-backports main" > /etc/apt/sources.list.d/stretch-backports.list
+echo "deb ${debian_mirror} testing main"           > /etc/apt/sources.list.d/testing.list
+printf "Package: *\nPin: release o=Debian,a=testing\nPin-Priority: -300\n" > /etc/apt/preferences.d/debian-testing
 
 dpkg --add-architecture i386