diff --git a/modules/upgrade-diff.nix b/modules/upgrade-diff.nix
new file mode 100644
index 0000000..d6a33f0
--- /dev/null
+++ b/modules/upgrade-diff.nix
@@ -0,0 +1,8 @@
+{pkgs, ...}: {
+  system.activationScripts.diff = {
+    supportsDryActivation = true;
+    text = ''
+      ${pkgs.nvd}/bin/nvd --nix-bin-dir=${pkgs.nix}/bin diff /run/current-system "$systemConfig"
+    '';
+  };
+}
diff --git a/outputs.nix b/outputs.nix
index 445116c..e660581 100644
--- a/outputs.nix
+++ b/outputs.nix
@@ -8,10 +8,12 @@
   ...
 } @ inputs: {
   nixosConfigurations = let
+    modulesDir = ./modules;
     defaultModules = [
       home-manager.nixosModules.home-manager
       ./common/fonts.nix
       ./packages/common.nix
+      ./modules/upgrade-diff.nix
 
       ({
         config,