diff --git a/pkgs/development/python-modules/service_identity/default.nix b/pkgs/development/python-modules/service_identity/default.nix
index d7c37e7c433b..8ac3b52d58c7 100644
--- a/pkgs/development/python-modules/service_identity/default.nix
+++ b/pkgs/development/python-modules/service_identity/default.nix
@@ -7,6 +7,7 @@
 , ipaddress
 , pyasn1
 , pyasn1-modules
+, six
 , pytestCheckHook
 , pythonOlder
 }:
@@ -28,6 +29,7 @@ buildPythonPackage rec {
     idna
     pyasn1
     pyasn1-modules
+    six
   ] ++ lib.optionals (pythonOlder "3.3") [
     ipaddress
   ];