diff --git a/tests/nixos/default.nix b/tests/nixos/default.nix
index 78f91ae1b..d8531b2c8 100644
--- a/tests/nixos/default.nix
+++ b/tests/nixos/default.nix
@@ -52,6 +52,11 @@ let
     );
   };
 
+  otherNixes.nix_2_18.setNixPackage = { lib, pkgs, ... }: {
+    imports = [ checkOverrideNixVersion ];
+    nix.package = lib.mkForce pkgs.nixVersions.nix_2_18;
+  };
+
 in
 
 {