diff --git a/pkgs/by-name/ni/nixos-rebuild-ng/package.nix b/pkgs/by-name/ni/nixos-rebuild-ng/package.nix
index e29b7d924149..020b9ae7694a 100644
--- a/pkgs/by-name/ni/nixos-rebuild-ng/package.nix
+++ b/pkgs/by-name/ni/nixos-rebuild-ng/package.nix
@@ -15,6 +15,13 @@
   # Very long tmp dirs lead to "too long for Unix domain socket"
   # SSH ControlPath errors. Especially macOS sets long TMPDIR paths.
   withTmpdir ? if stdenv.hostPlatform.isDarwin then "/tmp" else null,
+  # This version is kind of arbitrary, we use some features that were
+  # implemented in newer versions of Nix, but not necessary 2.18.
+  # However, Lix is a fork of Nix 2.18, so this looks like a good version
+  # to cut specific functionality.
+  # ATTN: This currently doesn't disambiguate between Nix and Lix, so using this
+  # in a conditional needs careful checking against both Nix implementations.
+  withNix218 ? lib.versionAtLeast nix.version "2.18",
   # passthru.tests
   nixosTests,
   nixVersions,
@@ -23,13 +30,6 @@
 }:
 let
   executable = if withNgSuffix then "nixos-rebuild-ng" else "nixos-rebuild";
-  # This version is kind of arbitrary, we use some features that were
-  # implemented in newer versions of Nix, but not necessary 2.18.
-  # However, Lix is a fork of Nix 2.18, so this looks like a good version
-  # to cut specific functionality.
-  # ATTN: This currently doesn't disambiguate between Nix and Lix, so using this
-  # in a conditional needs careful checking against both Nix implementations.
-  withNix218 = lib.versionAtLeast nix.version "2.18";
 in
 python3Packages.buildPythonApplication rec {
   pname = "nixos-rebuild-ng";