diff -ruN auth.orig/ldap_login.py auth.new/ldap_login.py
--- auth.orig/ldap_login.py	2009-04-01 16:34:54.000000000 +0200
+++ auth.new/ldap_login.py	2009-04-01 16:37:53.000000000 +0200
@@ -141,7 +141,7 @@
                         (ldap.OPT_X_TLS, self.start_tls),
                         #(ldap.OPT_X_TLS_ALLOW, 1),
                     ):
-                        if value is not None:
+                        if value not in (None, ''):
                             ldap.set_option(option, value)
 
                 server = self.server_uri