diff --git a/flake.nix b/flake.nix
index c228ef73..bc6912af 100644
--- a/flake.nix
+++ b/flake.nix
@@ -5,24 +5,29 @@
 
   nixConfig.extra-substituters = [ "https://nix-qchem.cachix.org" ];
 
-  outputs = { self, nixpkgs } : let
-      lib = import "${nixpkgs}/lib";
+  outputs = { self, nixpkgs, ... }:
+    let
+      qchemOvl = import ./overlay.nix;
+
+      system = "x86_64-linux";
 
       pkgs = (import nixpkgs) {
-        system = "x86_64-linux";
+        inherit system;
         overlays = [
-          (import ./overlay.nix)
-          (self: super: { qchem = super.qchem // {
-            turbomole = null;
-            cefine = null;
-            cfour = null;
-            mrcc = null;
-            orca = null;
-            qdng = null;
-            vmd = null;
-            mesa-qc = null;
-            mcdth = null;
-          };})
+          qchemOvl
+          (final: prev: {
+            qchem = prev.qchem // {
+              turbomole = null;
+              cefine = null;
+              cfour = null;
+              mrcc = null;
+              orca = null;
+              qdng = null;
+              vmd = null;
+              mesa-qc = null;
+              mcdth = null;
+            };
+          })
         ];
         config.allowUnfree = true;
         config.qchem-config = (import ./cfg.nix) {
@@ -31,17 +36,37 @@
         };
       };
 
-      pkgsClean = with lib; filterAttrs (n: isDerivation) pkgs.qchem;
-  in {
+      lib = pkgs.lib;
 
-    overlays = {
-      qchem = import ./overlay.nix;
-      pythonQchem = import ./pythonPackages.nix pkgs.config.qchem-config.prefix pkgs.config.qchem-config pkgs nixpkgs;
-      default = self.overlays.qchem;
-    };
+      # Cleaned package set, i.e. packages that
+      #  * build correctly
+      #  * are not insecure (thus, remove all python2 packages)
+      pkgsClean = with lib;
+        let
+          buildingPkgs = filterAttrs
+            (k: v:
+              if (v ? meta.broken)
+              then !(v.meta.broken) && isDerivation v
+              else isDerivation v
+            )
+            pkgs.qchem;
+          securePackages = builtins.removeAttrs buildingPkgs [ "python2" ];
+        in
+        securePackages;
+
+    in
+    {
+      packages."${system}" = pkgsClean;
+
+      hydraJobs."${system}" = pkgsClean;
 
-    packages."x86_64-linux" = pkgsClean;
-    hydraJobs."x86_64-linux" = pkgsClean;
-    checks."x86_64-linux" = with lib; filterAttrs (n: isDerivation) pkgs.qchem.tests;
-  };
+      checks."${system}" = with lib; filterAttrs (n: isDerivation) pkgs.qchem.tests;
+
+
+      overlays = {
+        qchem = qchemOvl;
+        pythonQchem = import ./pythonPackages.nix pkgs.config.qchem-config.prefix pkgs.config.qchem-config pkgs nixpkgs;
+        default = self.overlays.qchem;
+      };
+    };
 }
diff --git a/pythonPackages.nix b/pythonPackages.nix
index 25781b48..d9109215 100644
--- a/pythonPackages.nix
+++ b/pythonPackages.nix
@@ -1,21 +1,21 @@
-subset: cfg: selfPkgs: superPkgs: self: super:
+subset: cfg: finalPkgs: prevPkgs: final: prev:
 
 let
   callPackage = lib.callPackageWith (
-    selfPkgs.pkgs //  # nixpkgs
-    selfPkgs //       # overlay
-    self //           # python
+    finalPkgs.pkgs //  # nixpkgs
+    finalPkgs //       # overlay
+    final //           # python
     overlay );
 
-  inherit (selfPkgs.pkgs) lib;
+  inherit (finalPkgs.pkgs) lib;
 
   overlay = {
 
-  } // lib.optionalAttrs super.isPy3k {
+  } // lib.optionalAttrs prev.isPy3k {
     adcc = callPackage ./pkgs/apps/adcc { };
 
     dftbplus = callPackage ./pkgs/apps/dftbplus {
-      inherit (selfPkgs) tblite;
+      inherit (finalPkgs) tblite;
     };
 
     pyqdng = callPackage ./pkgs/apps/pyQDng { };
@@ -26,7 +26,7 @@ let
 
     moltemplate = callPackage ./pkgs/apps/moltemplate { };
 
-    openmm = superPkgs.openmm.override {
+    openmm = prevPkgs.openmm.override {
       enablePython = true;
       enableCuda = cfg.useCuda;
     };
@@ -40,13 +40,13 @@ let
     pylibefp = callPackage ./pkgs/lib/pylibefp { };
 
     psi4 = callPackage ./pkgs/apps/psi4 {
-      libint = superPkgs.libintPsi4;
+      libint = prevPkgs.libintPsi4;
     };
 
     pychemps2 = callPackage ./pkgs/apps/chemps2/PyChemMPS2.nix { };
 
     pysisyphus = callPackage ./pkgs/apps/pysisyphus {
-      gamess-us = selfPkgs.gamess-us.override {
+      gamess-us = finalPkgs.gamess-us.override {
         enableMpi = false;
       };
     };
@@ -54,8 +54,8 @@ let
     pyphspu = callPackage ./pkgs/lib/pyphspu { };
 
     tblite = callPackage ./pkgs/lib/tblite/python.nix {
-      inherit (selfPkgs) tblite;
-      inherit (superPkgs) meson;
+      inherit (finalPkgs) tblite;
+      inherit (prevPkgs) meson;
     };
 
     veloxchem = callPackage ./pkgs/apps/veloxchem { };
@@ -63,7 +63,7 @@ let
     vermouth = callPackage ./pkgs/apps/vermouth { };
 
     xtb-python = callPackage ./pkgs/lib/xtb-python { };
-  } // lib.optionalAttrs super.isPy27 {
+  } // lib.optionalAttrs prev.isPy27 {
     pyquante = callPackage ./pkgs/apps/pyquante { };
   };