diff --git a/NixOS.md b/NixOS.md
index 536dcd3..c607c98 100644
--- a/NixOS.md
+++ b/NixOS.md
@@ -13,6 +13,7 @@ This document contains general notes about NixOS that are independent of my NixO
     * [Add Home Manager with niv](#add-home-manager-with-niv)
     * [Add NUR with niv](#add-nur-with-niv)
   * [System information](#system-information)
+  * [Customize a NixOS package with override or nix-build](#customize-a-nixos-package-with-override-or-nix-build)
   * [Search for packages](#search-for-packages)
   * [Search for options](#search-for-options)
   * [Search which package owns a file](#search-which-package-owns-a-file)
@@ -137,6 +138,10 @@ nix-info -m
  - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`
 ```
 
+## Customize a NixOS package with override or nix-build
+
+See https://codeberg.org/privacy1st/nix-build-and-override-docs
+
 ## Search for packages
 
 * https://search.nixos.org/packages
diff --git a/modules/programs.nix b/modules/programs.nix
index 13c598b..581fa79 100644
--- a/modules/programs.nix
+++ b/modules/programs.nix
@@ -27,7 +27,7 @@
       gnome.gnome-disk-utility # Partition and format disks. Mount disk images (.ISO)
       gnome.gnome-calculator
 
-      #fractal # Matrix chat client.
+      #unstable.fractal # Matrix chat client.
       # Other Matrix clients.
       #   fluffychat
       #   Web version: https://app.cinny.in/