diff --git a/pkgs/development/interpreters/pypy/2.4/default.nix b/pkgs/development/interpreters/pypy/2.4/default.nix
index 8a6f2b61bb0..9799e810c6f 100644
--- a/pkgs/development/interpreters/pypy/2.4/default.nix
+++ b/pkgs/development/interpreters/pypy/2.4/default.nix
@@ -8,11 +8,11 @@ let
 
   majorVersion = "2.4";
   version = "${majorVersion}.0";
-  pythonVersion = "2.7";
   libPrefix = "pypy${majorVersion}";
 
   pypy = stdenv.mkDerivation rec {
     name = "pypy-${version}";
+    pythonVersion = "2.7";
 
     inherit majorVersion version;
 
diff --git a/pkgs/development/interpreters/python/2.6/default.nix b/pkgs/development/interpreters/python/2.6/default.nix
index 87e4dceee4d..9bf161ffc1a 100644
--- a/pkgs/development/interpreters/python/2.6/default.nix
+++ b/pkgs/development/interpreters/python/2.6/default.nix
@@ -56,6 +56,7 @@ let
   # external dependencies.
   python = stdenv.mkDerivation {
     name = "python${if includeModules then "" else "-minimal"}-${version}";
+    pythonVersion = majorVersion;
 
     inherit majorVersion version src patches buildInputs preConfigure;
 
diff --git a/pkgs/development/interpreters/python/2.7/default.nix b/pkgs/development/interpreters/python/2.7/default.nix
index 117d11f3052..0d7490d910c 100644
--- a/pkgs/development/interpreters/python/2.7/default.nix
+++ b/pkgs/development/interpreters/python/2.7/default.nix
@@ -55,6 +55,7 @@ let
   # external dependencies.
   python = stdenv.mkDerivation {
     name = "python-${version}";
+    pythonVersion = majorVersion;
 
     inherit majorVersion version src patches buildInputs preConfigure;
 
diff --git a/pkgs/development/interpreters/python/3.2/default.nix b/pkgs/development/interpreters/python/3.2/default.nix
index d3f5c6e1f13..2645b503344 100644
--- a/pkgs/development/interpreters/python/3.2/default.nix
+++ b/pkgs/development/interpreters/python/3.2/default.nix
@@ -27,6 +27,7 @@ let
 in
 stdenv.mkDerivation {
   name = "python3-${version}";
+  pythonVersion = majorVersion;
   inherit majorVersion version;
 
   src = fetchurl {
diff --git a/pkgs/development/interpreters/python/3.3/default.nix b/pkgs/development/interpreters/python/3.3/default.nix
index 1f91d1bbaf4..a8953f38245 100644
--- a/pkgs/development/interpreters/python/3.3/default.nix
+++ b/pkgs/development/interpreters/python/3.3/default.nix
@@ -20,6 +20,7 @@ with stdenv.lib;
 
 let
   majorVersion = "3.3";
+  pythonVersion = majorVersion;
   version = "${majorVersion}.6";
 
   buildInputs = filter (p: p != null) [
@@ -28,6 +29,7 @@ let
 in
 stdenv.mkDerivation {
   name = "python3-${version}";
+  pythonVersion = majorVersion;
   inherit majorVersion version;
 
   src = fetchurl {
diff --git a/pkgs/development/interpreters/python/3.4/default.nix b/pkgs/development/interpreters/python/3.4/default.nix
index 8c86f77ff75..5c99428463d 100644
--- a/pkgs/development/interpreters/python/3.4/default.nix
+++ b/pkgs/development/interpreters/python/3.4/default.nix
@@ -20,6 +20,7 @@ with stdenv.lib;
 
 let
   majorVersion = "3.4";
+  pythonVersion = majorVersion;
   version = "${majorVersion}.2";
   fullVersion = "${version}";
 
@@ -29,6 +30,7 @@ let
 in
 stdenv.mkDerivation {
   name = "python3-${fullVersion}";
+  pythonVersion = majorVersion;
   inherit majorVersion version;
 
   src = fetchurl {
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index 12d233ad332..c3a9455f014 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -3,6 +3,8 @@
 with pkgs.lib;
 
 let
+  pythonAtLeast = versionAtLeast python.pythonVersion;
+  pythonOlder = versionOlder python.pythonVersion;
   isPy26 = python.majorVersion == "2.6";
   isPy27 = python.majorVersion == "2.7";
   isPy33 = python.majorVersion == "3.3";
@@ -2995,7 +2997,7 @@ let
     name = "pew-0.1.14";
     namePrefix = "";
 
-    disabled = isPy26 || isPy27 || isPy33; # old versions require backported libraries
+    disabled = pythonOlder "3.4"; # old versions require backported libraries
 
     src = pkgs.fetchurl {
       url = "https://pypi.python.org/packages/source/p/pew/${name}.tar.gz";