diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index 6401f931fd7..a0025936647 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -8254,8 +8254,9 @@ in {
         pytestflakes
         pytestpep8
         mock
-        pathlib
-      ];
+      ]
+      # pathlib was made part of standard library in 3.5:
+      ++ (optionals (pythonOlder "3.4") [ pathlib ]);
 
     meta = {
       description = "Natural sorting for python";