diff --git a/debug/build_overrides.nix b/debug/build_overrides.nix
index 4f4dd2d..1b5a4af 100644
--- a/debug/build_overrides.nix
+++ b/debug/build_overrides.nix
@@ -1,14 +1,8 @@
 let
-  nixpkgs_commit = builtins.readFile ../mach_nix/nix/NIXPKGS_COMMIT;  # nixpkgs version to use python packages from
-  nixpkgs_tarball_sha256 = builtins.readFile ../mach_nix/nix/NIXPKGS_SHA256;
-  pkgs = import (builtins.fetchTarball {
-    name = "nixpkgs";
-    url = "https://github.com/nixos/nixpkgs/tarball/${builtins.readFile ../mach_nix/nix/NIXPKGS_COMMIT}";
-    sha256 = "${builtins.readFile ../mach_nix/nix/NIXPKGS_SHA256}";
-  }) { config = {}; overlays = []; };
+  pkgs = import (import ../mach_nix/nix/nixpkgs-src.nix) { config = {}; overlays = []; };
   python = pkgs.python37;
   manylinux1 = [ pkgs.pythonManylinuxPackages.manylinux1 ];
-  result = import ./overrides.nix;
+  result = import ./overrides.nix { inherit pkgs python; };
   overrides = result.overrides manylinux1 pkgs.autoPatchelfHook;
   py = pkgs.python37.override { packageOverrides = overrides; };
 in
diff --git a/flake.nix b/flake.nix
index acd2c3a..d9ac192 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,7 +3,7 @@
   description = "Create highly reproducible python environments";
 
   inputs.flake-utils.url = "github:numtide/flake-utils";
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/873c294e03c";
   inputs.pypi-deps-db = {
     url = "github:DavHau/pypi-deps-db";
     flake = false;
diff --git a/mach_nix/flake.lock b/mach_nix/flake.lock
index 865551b..8d8d9ec 100644
--- a/mach_nix/flake.lock
+++ b/mach_nix/flake.lock
@@ -17,16 +17,16 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1615259932,
-        "narHash": "sha256-IXecmbqCr+XCtFwzBO3tHEd8PoJ4X4EyPZebKbV2ioE=",
+        "lastModified": 1621687574,
+        "narHash": "sha256-d5GSlJC3fJqsq0nfaBrB3vN3Am2+E0AhqC6ZWS2a4qs=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "29b0d4d0b600f8f5dd0b86e3362a33d4181938f9",
+        "rev": "873c294e03ccefb4ef4693a6a6258a2c75d44b80",
         "type": "github"
       },
       "original": {
         "owner": "NixOS",
-        "ref": "nixos-unstable",
+        "ref": "873c294e03c",
         "repo": "nixpkgs",
         "type": "github"
       }
diff --git a/mach_nix/generators/overides_generator.py b/mach_nix/generators/overides_generator.py
index 970b341..51cfee5 100644
--- a/mach_nix/generators/overides_generator.py
+++ b/mach_nix/generators/overides_generator.py
@@ -264,7 +264,13 @@ class OverridesGenerator(ExpressionGenerator):
                 url = "{src_url}";
                 sha256 = "{src_sha256}";
               }};
-              format = "condabin";
+              format = "other";
+              nativeBuildInputs = with python.pkgs; [
+                autoPatchelfHook
+                condaUnpackHook
+                condaInstallHook
+              ];
+              buildInputs = pkgs.pythonCondaPackages.condaPatchelfLibs;
               passthru = (get_passthru "{name}" "{nix_name}") // {{ 
                 provider = "conda";
                 allCondaDeps = allCondaDepsRec pSelf;
diff --git a/mach_nix/nix/buildPythonPackage.nix b/mach_nix/nix/buildPythonPackage.nix
index 99bd81f..02a4a26 100644
--- a/mach_nix/nix/buildPythonPackage.nix
+++ b/mach_nix/nix/buildPythonPackage.nix
@@ -61,7 +61,6 @@ let
       };
       py_final = python_pkg.override { packageOverrides = l.mergeOverrides (
         overridesPre
-        ++ [ (import ./mk-python-derivation-overlay.nix pkgs python_pkg) ]
         ++ [ result.overrides ]
         ++ (l.fixes_to_overrides _fixes)
         ++ overridesPost ++ (l.simple_overrides _)
diff --git a/mach_nix/nix/mk-python-derivation-overlay.nix b/mach_nix/nix/mk-python-derivation-overlay.nix
index b1d2351..021cc74 100644
--- a/mach_nix/nix/mk-python-derivation-overlay.nix
+++ b/mach_nix/nix/mk-python-derivation-overlay.nix
@@ -27,18 +27,22 @@ pkgs: python: with pkgs.lib;
   in
   pySelf: pySuper: {
     buildPythonPackage = makeOverridablePythonPackage (
-      makeOverridable (callPackage ./from-nixpkgs/mk-python-derivation.nix {
+      makeOverridable (callPackage "${pkgs.path}/pkgs/development/interpreters/python/mk-python-derivation.nix" {
         inherit namePrefix;     # We want Python libraries to be named like e.g. "python3.6-${name}"
         inherit toPythonModule; # Libraries provide modules
-        autoPatchelfHook = callPackage ./auto_patchelf_hook.nix {};
+
+        # this prevents infinite recursions when overriding setuptools later
+        setuptools = python.pkgs.setuptools;
       })
     );
 
     buildPythonApplication = makeOverridablePythonPackage (
-      makeOverridable (callPackage ./from-nixpkgs/mk-python-derivation.nix {
+      makeOverridable (callPackage "${pkgs.path}/pkgs/development/interpreters/python/mk-python-derivation.nix" {
         namePrefix = "";        # Python applications should not have any prefix
         toPythonModule = x: x;  # Application does not provide modules.
-        autoPatchelfHook = callPackage ./auto_patchelf_hook.nix {};
+
+        # this prevents infinite recursions when overriding setuptools later
+        setuptools = python.pkgs.setuptools;
       })
     );
   }
diff --git a/mach_nix/nix/mkPython.nix b/mach_nix/nix/mkPython.nix
index b189624..d047e44 100644
--- a/mach_nix/nix/mkPython.nix
+++ b/mach_nix/nix/mkPython.nix
@@ -112,7 +112,6 @@ let
       all_overrides = l.mergeOverrides (
         overridesPre ++ overrides_pre_extra
         ++ extra_pkgs_py_overrides
-        ++ [ (import ./mk-python-derivation-overlay.nix pkgs python_pkg) ]
         ++ [ result.overrides ]
         ++ (l.fixes_to_overrides _fixes)
         ++ overrides_post_extra ++ overridesPost