diff --git a/source/_posts/cloudflare-argo-nixos.md b/source/_posts/cloudflare-argo-nixos.md
index a351c07..499e5a2 100644
--- a/source/_posts/cloudflare-argo-nixos.md
+++ b/source/_posts/cloudflare-argo-nixos.md
@@ -104,6 +104,13 @@ in {
         The data directory, for storing credentials.
       '';
     };
+
+    package = mkOption {
+      default = pkgs.cloudflared;
+      defaultText = "pkgs.cloudflared";
+      type = types.package;
+      description = "cloudflared package to use.";
+    };
   };
 
   config = mkIf cfg.enable {
@@ -113,7 +120,7 @@ in {
       wants = [ "network-online.target" ]; # systemd-networkd-wait-online.service
       wantedBy = [ "multi-user.target" ];
       serviceConfig = {
-        ExecStart = "${pkgs.cloudflared}/bin/cloudflared --config ${cfg.config} --no-autoupdate tunnel run";
+        ExecStart = "${cfg.package}/bin/cloudflared --config ${cfg.config} --no-autoupdate tunnel run";
         Type = "simple";
         User = "argoWeb";
         Group = "argoWeb";
@@ -163,9 +170,12 @@ Restart/reload Caddy for the changed config to take effect.
   ];
   # cloudflared is not distributed via a free software license
   nixpkgs.config.allowUnfree = true;
-  services.argoWeb.enable = true;
-  # if the config is in another location
-  # services.argoWeb.config = "/etc/caddy/argoWeb.yml";
+  services.argoWeb = {
+    enable = true;
+    config = "/etc/caddy/argoWeb.yml";
+    # custom package
+    # package = pkgs.callPackage (import /etc/caddy/cloudflared-custom.nix) { };
+  };
 ```
 
 ## Create a CNAME record
diff --git a/source/_posts/custom-package-nixos-module.md b/source/_posts/custom-package-nixos-module.md
new file mode 100644
index 0000000..aab846c
--- /dev/null
+++ b/source/_posts/custom-package-nixos-module.md
@@ -0,0 +1,91 @@
+---
+title: Using custom package in a NixOS module
+excerpt: A workaround for installing GitHub-hosted package in a IPv6-only host
+date: 2021-07-02
+tags:
+- nixos
+---
+
+I recently setup {% post_link cloudflare-argo-nixos 'cloudflared' %} on instances that power this website, while I got it working on most of them, it's not working on IPv6-only instance. There was installation guide which I managed to resolve later (and what this post is about) and Cloudflare tunnel itself [doesn't support](https://github.com/cloudflare/cloudflared/issues/401) IPv6 yet.
+
+A quick recap on two of the main components of NixOS: module and package. A package is a program that is available on NixOS repository, the repo doesn't contain the binary, it's made up of nix files that describe _how_ to compile it. In this case, [cloudflared.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/cloudflared/default.nix) is a script to download the source code from [GitHub](https://github.com/cloudflare/cloudflared) and compile it as a Go program.
+
+A module is (usually) used to install a program as a service and make it configurable via `configuration.nix`. For example, [i2pd.nix](https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/networking/i2pd.nix) module installs i2pd package ([`pkgs.i2pd`](https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/networking/i2pd/default.nix)) when `services.i2pd.enable` is enabled.
+
+A major issue is that GitHub [doesn't support](https://github.community/t/github-on-the-ipv6-internet/2794/14) IPv6 yet, so my IPv6-only instance couldn't download the source code. A common workaround is to mirror the repo somewhere else that does support IPv6, which is what I did. Then, I created a new custom package nix:
+
+{% codeblock cloudflared-custom.nix lang:nix https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/cloudflared/default.nix source mark:8 %}
+{ lib, buildGoModule, fetchgit }:
+
+buildGoModule rec {
+  pname = "cloudflared";
+  version = "2021.6.0";
+
+  src = fetchgit {
+    url    = "https://example.com/example/cloudflared-mirror.git";
+    rev    = "refs/tags/${version}";
+    sha256 = "sha256-cX0kdBPDgwjHphxGWrnXohHPp1nzs4SnvCry4AxMtp0=";
+  };
+
+  vendorSha256 = null;
+
+  doCheck = false;
+
+  buildFlagsArray = "-ldflags=-X main.Version=${version}";
+
+  meta = with lib; {
+    description = "CloudFlare Argo Tunnel daemon (and DNS-over-HTTPS client)";
+    homepage    = "https://www.cloudflare.com/products/argo-tunnel";
+    license     = licenses.unfree;
+    platforms   = platforms.unix;
+    maintainers = [ maintainers.thoughtpolice maintainers.enorris ];
+  };
+}
+{% endcodeblock %}
+
+In my {% post_link clouflared-argo-nixos 'cloudflared module' %}, I updated the following lines:
+
+``` diff
+  options.services.argoWeb = {
+    enable = mkEnableOption "Cloudflare Argo Tunnel";
+
+    config = mkOption {
+      default = "/etc/caddy/argoWeb.yml";
+      type = types.str;
+      description = "Path to cloudflared config";
+    };
+
+    dataDir = mkOption {
+      default = "/var/lib/argoWeb";
+      type = types.path;
+      description = ''
+        The data directory, for storing credentials.
+      '';
+    };
+
++    package = mkOption {
++      default = pkgs.cloudflared;
++      defaultText = "pkgs.cloudflared";
++      type = types.package;
++      description = "cloudflared package to use.";
++    };
+  };
+
+-        ExecStart = "${pkgs.cloudflared}/bin/cloudflared --config ${cfg.config} --no-autoupdate tunnel run";
++        ExecStart = "${cfg.package}/bin/cloudflared --config ${cfg.config} --no-autoupdate tunnel run";
+```
+
+Finally, in my `configuration.nix`, I configured it to use the custom package:
+
+``` diff
+  require = [
+    /etc/caddy/argoWeb.nix
+  ];
+
+  nixpkgs.config.allowUnfree = true;
+  services.argoWeb = {
+    enable = true;
++    package = pkgs.callPackage (import /etc/caddy/cloudflared-custom.nix) { };
+    config = "/etc/caddy/argoWeb.yml";
+  };
+```