diff --git a/pkgs/development/python-modules/psutil/default.nix b/pkgs/development/python-modules/psutil/default.nix
index 4181f582c75..89797c4802c 100644
--- a/pkgs/development/python-modules/psutil/default.nix
+++ b/pkgs/development/python-modules/psutil/default.nix
@@ -3,6 +3,7 @@
 , pytest
 , mock
 , ipaddress
+, unittest2
 }:
 
 buildPythonPackage rec {
@@ -18,7 +19,7 @@ buildPythonPackage rec {
   # tests segfaults on darwin https://github.com/giampaolo/psutil/issues/1715
   doCheck = !stdenv.isDarwin && stdenv.isx86_64;
   checkInputs = [ pytest ]
-    ++ lib.optionals isPy27 [ mock ipaddress ];
+    ++ lib.optionals isPy27 [ mock ipaddress unittest2 ];
   # out must be referenced as test import paths are relative
   # disable tests which don't work in sandbox
   # cpu_times is flakey on darwin