diff --git a/pkgs/development/python-modules/python-ptrace/default.nix b/pkgs/development/python-modules/python-ptrace/default.nix
index e9fafd9b99a..426b956880a 100644
--- a/pkgs/development/python-modules/python-ptrace/default.nix
+++ b/pkgs/development/python-modules/python-ptrace/default.nix
@@ -1,6 +1,7 @@
 { stdenv
 , buildPythonPackage
 , fetchPypi
+, six
 }:
 
 buildPythonPackage rec {
@@ -15,6 +16,8 @@ buildPythonPackage rec {
   # requires distorm, which is optionally
   doCheck = false;
 
+  propagatedBuildInputs = [ six ];
+
   meta = with stdenv.lib; {
     description = "Python binding of ptrace library";
     homepage = https://github.com/vstinner/python-ptrace;