diff --git a/auth/credentials/pycredentials.c b/auth/credentials/pycredentials.c
index 165f8031e70..fee9556b180 100644
--- a/auth/credentials/pycredentials.c
+++ b/auth/credentials/pycredentials.c
@@ -90,16 +90,19 @@ static PyObject *py_creds_get_ntlm_response(PyObject *self, PyObject *args, PyOb
 	DATA_BLOB lm_session_key = data_blob_null;
 	DATA_BLOB nt_session_key = data_blob_null;
 	const char *kwnames[] = { "flags", "challenge",
-				  "target_info", "server_timestamp",
+				  "target_info",
 				  NULL };
 
 	tv_now = timeval_current();
 	server_timestamp = timeval_to_nttime(&tv_now);
 
-	if (!PyArg_ParseTupleAndKeywords(args, kwargs,
-					 "i" PYARG_BYTES_LEN "|" PYARG_BYTES_LEN "K",
+	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "is#|s#",
 					 discard_const_p(char *, kwnames),
-					 &flags, &challenge, &target_info.data, &target_info.length)) {
+					 &flags,
+					 &challenge.data,
+					 &challenge.length,
+					 &target_info.data,
+					 &target_info.length)) {
 		return NULL;
 	}
 
diff --git a/selftest/flapping b/selftest/flapping
index 50fdf1ed972..e40a2ab2d4d 100644
--- a/selftest/flapping
+++ b/selftest/flapping
@@ -34,3 +34,4 @@
 ^samba3.blackbox.smbclient_tar.* # fails very, very often on sn-devel
 ^samba3.blackbox.smbclient_s3.*.sending a message to the remote server # flakey on sn-devel-104 and sn-devel-144
 ^samba3.blackbox.smbclient_s3.*.creating a good symlink and deleting it by path # flakey on sn-devel-104 and sn-devel-144
+^samba.tests.auth_log_samlogon
diff --git a/selftest/knownfail b/selftest/knownfail
index 44757c3004d..b16ff520e42 100644
--- a/selftest/knownfail
+++ b/selftest/knownfail
@@ -330,5 +330,3 @@
 # We currently don't send referrals for LDAP modify of non-replicated attrs
 ^samba4.ldap.rodc.python\(rodc\).__main__.RodcTests.test_modify_nonreplicated.*
 ^samba4.ldap.rodc_rwdc.python.*.__main__.RodcRwdcTests.test_change_password_reveal_on_demand_kerberos
-# samba.tests.auth_log_samlogon should fail until all the fixes are applied
-^samba.tests.auth_log_samlogon