diff --git a/misc/build.func b/misc/build.func
index 9024d10b8..acf2e3ccb 100644
--- a/misc/build.func
+++ b/misc/build.func
@@ -1338,6 +1338,9 @@ EOF'
       msg_warn "Skipping timezone setup – zone '$tz' not found in container"
     fi
 
+    pct exec "$CTID" -- bash -c "echo deb https://archive.debian.org/debian buster main contrib >/etc/apt/sources.list"
+    pct exec "$CTID" -- bash -c "echo deb https://archive.debian.org/debian buster-updates main contrib >>/etc/apt/sources.list"
+    pct exec "$CTID" -- bash -c "echo deb https://archive.debian.org/debian-security buster/updates main contrib >>/etc/apt/sources.list"
     pct exec "$CTID" -- bash -c "apt-get update >/dev/null && apt-get install -y sudo curl mc gnupg2 jq >/dev/null"
   fi
   msg_ok "Customized LXC Container"