diff --git a/nixos/modules/misc/nixpkgs.nix b/nixos/modules/misc/nixpkgs.nix
index 5bd7eb1408b2..00460a88d86c 100644
--- a/nixos/modules/misc/nixpkgs.nix
+++ b/nixos/modules/misc/nixpkgs.nix
@@ -358,7 +358,7 @@ in
             else "nixpkgs.localSystem";
           pkgsSystem = finalPkgs.stdenv.targetPlatform.system;
         in {
-          assertion = !hasPlatform -> nixosExpectedSystem == pkgsSystem;
+          assertion = constructedByMe -> !hasPlatform -> nixosExpectedSystem == pkgsSystem;
           message = "The NixOS nixpkgs.pkgs option was set to a Nixpkgs invocation that compiles to target system ${pkgsSystem} but NixOS was configured for system ${nixosExpectedSystem} via NixOS option ${nixosOption}. The NixOS system settings must match the Nixpkgs target system.";
         }
       )