diff --git a/modules/nix/nixpkgs.nix b/modules/nix/nixpkgs.nix
index ee999971..511d718c 100644
--- a/modules/nix/nixpkgs.nix
+++ b/modules/nix/nixpkgs.nix
@@ -284,7 +284,7 @@ in
           pkgsSystem = finalPkgs.stdenv.targetPlatform.system;
         in {
           assertion = cfg.constructedByUs -> !hasPlatform -> cfg.system == pkgsSystem;
-          message = "The nix-darwin nixpkgs.pkgs option was set to a Nixpkgs invocation that compiles to target system ${pkgsSystem} but nix-darwin was configured for system ${darwinExpectedSystem} via nix-darwin option nixpkgs.system. The nix-darwin system settings must match the Nixpkgs target system.";
+          message = "The nix-darwin nixpkgs.pkgs option was set to a Nixpkgs invocation that compiles to target system ${pkgsSystem} but nix-darwin was configured for system ${config.nixpkgs.system} via nix-darwin option nixpkgs.system. The nix-darwin system settings must match the Nixpkgs target system.";
         }
       )
       {