diff --git a/cad/default.nix b/cad/default.nix
index 6d7a890..928f0ee 100644
--- a/cad/default.nix
+++ b/cad/default.nix
@@ -155,8 +155,8 @@
           };
 
           # Formatter for nix files, available through 'nix fmt'
-          treefmt = lib.mkIf cfg.formatter.enable {
-            programs.alejandra.enable = lib.mkIf cfg.formatter.nix true;
+          treefmt.programs = lib.mkIf cfg.formatter.enable {
+            alejandra.enable = lib.mkIf cfg.formatter.nix true;
           };
         };
       });