diff --git a/nix/configurations/hetzner_benchmark.nix b/nix/configurations/hetzner_benchmark.nix
index 2fddb026..6201e6f1 100644
--- a/nix/configurations/hetzner_benchmark.nix
+++ b/nix/configurations/hetzner_benchmark.nix
@@ -31,6 +31,9 @@ in
     # nixpkgs
     #
     {
+      # don't use `nixpkgs.flake.source`, it uses flake so it double fetches
+      nix.nixPath = [ "nixpkgs=${sources.nixpkgs}" ];
+
       nixpkgs = {
         overlays = map import [
           ../packages/overlay.nix
@@ -39,10 +42,6 @@ in
           ../overlays/lix.nix
           ../overlays/nix-monitored.nix
         ];
-
-        # Set NIX_PATH and flake registry at the same time
-        # https://github.com/NixOS/nixpkgs/pull/254405
-        flake.source = sources.nixpkgs;
       };
 
       nix.package = pkgs.nix-monitored;
diff --git a/nix/configurations/hydrogen.nix b/nix/configurations/hydrogen.nix
index c751ef0a..5a303423 100644
--- a/nix/configurations/hydrogen.nix
+++ b/nix/configurations/hydrogen.nix
@@ -34,6 +34,9 @@ in
     # nixpkgs
     #
     {
+      # don't use `nixpkgs.flake.source`, it uses flake so it double fetches
+      nix.nixPath = [ "nixpkgs=${sources.nixpkgs}" ];
+
       nixpkgs = {
         overlays = map import [
           ../overlays/agenix.nix
@@ -45,10 +48,6 @@ in
           ../overlays/lix.nix
           ../overlays/nix-monitored.nix
         ];
-
-        # Set NIX_PATH and flake registry at the same time
-        # https://github.com/NixOS/nixpkgs/pull/254405
-        flake.source = sources.nixpkgs;
       };
 
       nix.package = pkgs.nix-monitored;
diff --git a/nix/configurations/vanadium.nix b/nix/configurations/vanadium.nix
index 2fba0b2a..f881d389 100644
--- a/nix/configurations/vanadium.nix
+++ b/nix/configurations/vanadium.nix
@@ -35,6 +35,9 @@ in
       nix = {
         distributedBuilds = true;
         settings.builders-use-substitutes = true;
+
+        # don't use `nixpkgs.flake.source`, it uses flake so it double fetches
+        nixPath = [ "nixpkgs=${sources.nixpkgs}" ];
       };
 
       nixpkgs = {
@@ -70,10 +73,6 @@ in
           ../overlays/lix.nix
           ../overlays/nix-monitored.nix
         ];
-
-        # Set NIX_PATH and flake registry at the same time
-        # https://github.com/NixOS/nixpkgs/pull/254405
-        flake.source = sources.nixpkgs;
       };
 
       nix.package = pkgs.nix-monitored;