diff --git a/ops/nixos/lib/common.nix b/ops/nixos/lib/common.nix
index f3520bd91d..f0cb90692f 100644
--- a/ops/nixos/lib/common.nix
+++ b/ops/nixos/lib/common.nix
@@ -85,7 +85,7 @@ in
 
   # Clean up daily.
   nix.gc = {
-    automatic = true;
+    automatic = lib.mkDefault true;
     dates = "*-*-* 05:00:00";
   };
 }