diff --git a/nixos/modules/services/printing/cups-pdf.nix b/nixos/modules/services/printing/cups-pdf.nix
index ccb5f4963e9c4..25c5fb8a89b1b 100644
--- a/nixos/modules/services/printing/cups-pdf.nix
+++ b/nixos/modules/services/printing/cups-pdf.nix
@@ -42,12 +42,14 @@ let
   instanceSettings = name: {
     freeformType =
       with lib.types;
-      nullOr (oneOf [
-        int
-        str
-        path
-        package
-      ]);
+      attrsOf (
+        nullOr (oneOf [
+          int
+          str
+          path
+          package
+        ])
+      );
     # override defaults:
     # inject instance name into paths,
     # also avoid conflicts between user names and special dirs