diff --git a/modules/base.nix b/modules/base.nix
index 2ba9864..a999ae3 100755
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -6,6 +6,13 @@
     '';
   };
 
+  system.activationScripts.report-nixos-changes = ''
+    if [ -e /run/current-system ] && [ -e $systemConfig ]; then
+      echo System package diff:
+      ${config.nix.package}/bin/nix store diff-closures /run/current-system $systemConfig || true
+    fi
+  '';
+
   # Select internationalisation properties.
   i18n.defaultLocale = "en_US.UTF-8";
   console = {