diff --git a/common.nix b/common.nix
index 5cf1757..b077b10 100644
--- a/common.nix
+++ b/common.nix
@@ -29,6 +29,8 @@ all: {
     lib.mkDefault "idle";
 
   nix = {
+    optimise.automatic = true;
+
     gc = {
       automatic = lib.mkDefault true;
       dates = lib.mkDefault "20:00";