diff --git a/pkgs/testing/flake-module.nix b/pkgs/testing/flake-module.nix
index c30aaf383..05f4c53cb 100644
--- a/pkgs/testing/flake-module.nix
+++ b/pkgs/testing/flake-module.nix
@@ -37,6 +37,11 @@
             setuptools
             wheel
           ];
+          postPatch = ''
+            substituteInPlace nixos_test_lib/nix_setup.py \
+              --replace '@cp@' '${pkgs.coreutils}/bin/cp' \
+              --replace '@nix-store@' '${pkgs.nix}/bin/nix-store'
+          '';
           doCheck = false;
         };
 
diff --git a/pkgs/testing/nixos_test_lib/nix_setup.py b/pkgs/testing/nixos_test_lib/nix_setup.py
index b42126b44..a8ed4d72d 100644
--- a/pkgs/testing/nixos_test_lib/nix_setup.py
+++ b/pkgs/testing/nixos_test_lib/nix_setup.py
@@ -4,6 +4,10 @@ import os
 import subprocess
 from pathlib import Path
 
+# These paths will be substituted during package build
+CP_BIN = "@cp@"
+NIX_STORE_BIN = "@nix-store@"
+
 
 def setup_nix_in_nix(closure_info: str | None) -> None:
     """Set up Nix store inside test environment
@@ -44,7 +48,7 @@ def setup_nix_in_nix(closure_info: str | None) -> None:
             # Copy store paths to test store using external cp command
             # (handles symlinks better)
             subprocess.run(
-                ["cp", "--recursive", "--target", f"{tmpdir}/store"]
+                [CP_BIN, "--recursive", "--target", f"{tmpdir}/store"]
                 + [path.strip() for path in store_paths if path.strip()],
                 check=True,
             )
@@ -57,7 +61,7 @@ def setup_nix_in_nix(closure_info: str | None) -> None:
 
                 with registration_file.open() as f:
                     subprocess.run(
-                        ["nix-store", "--load-db"],
+                        [NIX_STORE_BIN, "--load-db"],
                         input=f.read(),
                         text=True,
                         env=env,