diff --git a/pkgs/development/python-modules/ldaptor/default.nix b/pkgs/development/python-modules/ldaptor/default.nix
index 2a4550d6b42..e3694bffe37 100644
--- a/pkgs/development/python-modules/ldaptor/default.nix
+++ b/pkgs/development/python-modules/ldaptor/default.nix
@@ -3,12 +3,13 @@
 , fetchPypi
 , twisted
 , passlib
-, pycrypto
 , pyopenssl
 , pyparsing
 , service-identity
 , zope_interface
 , isPy3k
+, pythonAtLeast
+, python
 }:
 
 buildPythonPackage rec {
@@ -21,13 +22,15 @@ buildPythonPackage rec {
   };
 
   propagatedBuildInputs = [
-    twisted passlib pycrypto pyopenssl pyparsing service-identity zope_interface
+    twisted passlib pyopenssl pyparsing service-identity zope_interface
   ];
 
-  disabled = isPy3k;
+  # https://github.com/twisted/ldaptor/pull/210
+  disabled = !isPy3k || pythonAtLeast "3.9";
 
-  # TypeError: None is neither bytes nor unicode
-  doCheck = false;
+  checkPhase = ''
+    ${python.interpreter} -m twisted.trial ldaptor
+  '';
 
   meta = {
     description = "A Pure-Python Twisted library for LDAP";
diff --git a/pkgs/development/python-modules/privacyidea/ldap-proxy.nix b/pkgs/development/python-modules/privacyidea/ldap-proxy.nix
index ec87186a4fd..25a81510c7d 100644
--- a/pkgs/development/python-modules/privacyidea/ldap-proxy.nix
+++ b/pkgs/development/python-modules/privacyidea/ldap-proxy.nix
@@ -1,9 +1,12 @@
-{ lib, buildPythonPackage, fetchFromGitHub, twisted, ldaptor, configobj }:
+{ lib, buildPythonPackage, isPy3k, fetchFromGitHub, twisted, ldaptor, configobj }:
 
 buildPythonPackage rec {
   pname = "privacyidea-ldap-proxy";
   version = "0.6.1";
 
+  # https://github.com/privacyidea/privacyidea-ldap-proxy/issues/50
+  disabled = isPy3k;
+
   src = fetchFromGitHub {
     owner = "privacyidea";
     repo = pname;