diff --git a/Dockerfile b/Dockerfile
index 2c1bf42..594b0b7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,7 +4,7 @@ ARG USERNAME_TO_ADD=user
 ARG UID_TO_ADD=1000
 ARG GID_TO_ADD=1000
 
-ARG UBUNTU_MIRROR_URL=http://us.archive.ubuntu.com/ubuntu
+ARG UBUNTU_MIRROR_URL=mirror://mirrors.ubuntu.com/mirrors.txt
 
 # setup
 ADD ./run.sh /tmp/run.sh
diff --git a/run.sh b/run.sh
index 7ac6f27..68f8f3f 100644
--- a/run.sh
+++ b/run.sh
@@ -6,18 +6,12 @@ set -e
 exec 1> >(tee -a /var/log/sandboxbuild.log) 2>&1
 
 MURM="main universe restricted multiverse"
-M="http://us.archive.ubuntu.com/ubuntu"
 C="$(lsb_release -cs)"
-
-if [[ ! -z "$UBUNTU_MIRROR_URL" ]]; then
-    M="$UBUNTU_MIRROR_URL"
-fi
-
 cat > /etc/apt/sources.list.new <<EOF
-deb $M $C $MURM
-deb $M $C-updates $MURM
-deb $M $C-backports $MURM
-deb $M $C-security $MURM
+deb $UBUNTU_MIRROR_URL $C $MURM
+deb $UBUNTU_MIRROR_URL $C-updates $MURM
+deb $UBUNTU_MIRROR_URL $C-backports $MURM
+deb $UBUNTU_MIRROR_URL $C-security $MURM
 EOF
 
 PKGS="