diff --git a/pkgs/development/python-modules/aniso8601/default.nix b/pkgs/development/python-modules/aniso8601/default.nix
index b637f60696d..4f660239530 100644
--- a/pkgs/development/python-modules/aniso8601/default.nix
+++ b/pkgs/development/python-modules/aniso8601/default.nix
@@ -1,5 +1,5 @@
 { stdenv, buildPythonPackage, fetchPypi
-, dateutil }:
+, dateutil, mock, isPy3k }:
 
 buildPythonPackage rec {
   pname = "aniso8601";
@@ -13,6 +13,8 @@ buildPythonPackage rec {
 
   propagatedBuildInputs = [ dateutil ];
 
+  checkInputs = stdenv.lib.optional (!isPy3k) mock;
+
   src = fetchPypi {
     inherit pname version;
     sha256 = "1x49k287ky1spv3msc9fwmc7ydyw6rlcr14nslgcmpjfn3pgzh03";