diff --git a/flake.nix b/flake.nix
index fb700847..a1c5a9da 100644
--- a/flake.nix
+++ b/flake.nix
@@ -140,7 +140,7 @@
         }
         // inputs;
       base_args = {
-        inherit nix-darwin home-manager system specialArgs;
+        inherit nix-darwin home-manager system specialArgs nixpkgs;
       };
     in {
       harmonica = macosSystem (base_args // {
diff --git a/lib/macosSystem.nix b/lib/macosSystem.nix
index 4161b0e7..927349ff 100644
--- a/lib/macosSystem.nix
+++ b/lib/macosSystem.nix
@@ -1,4 +1,5 @@
 {
+  nixpkgs,
   nix-darwin,
   home-manager,
   system,
@@ -13,6 +14,15 @@ in
     modules =
       darwin-modules
       ++ [
+        {
+          # make `nix run nixpkgs#nixpkgs` use the same nixpkgs as the one used by this flake.
+          nix.registry.nixpkgs.flake = nixpkgs;
+
+          # make `nix repl '<nixpkgs>'` use the same nixpkgs as the one used by this flake.
+          environment.etc."nix/inputs/nixpkgs".source = "${nixpkgs}";
+          nix.nixPath = ["/etc/nix/inputs"];
+        }
+
         home-manager.darwinModules.home-manager
         {
           home-manager.useGlobalPkgs = true;