diff --git a/modules/base.nix b/modules/base.nix
index 2e5bf99..9834f8f 100644
--- a/modules/base.nix
+++ b/modules/base.nix
@@ -39,8 +39,13 @@
   # NixOS state version (see https://nixos.wiki/wiki/FAQ/When_do_I_update_stateVersion)
   system.stateVersion = "20.03";
 
-  # Make sudoers trusted nix users
-  nix.trustedUsers = [ "@wheel" ];
+  nix = {
+    # Make sudoers trusted nix users
+    trustedUsers = [ "@wheel" ];
+
+    # On-the-fly optimisation of nix store
+    autoOptimiseStore = true;
+  };
 
   nixpkgs.config = {
     # Explicitly allow unfree packages (rule of thumb: assets ok, code not ok)