diff --git a/sysmocom/suites/nitb_smpp/esme_ms_sms_storeforward.py b/sysmocom/suites/nitb_smpp/esme_ms_sms_storeforward.py
index f9617e2..f4d379c 100755
--- a/sysmocom/suites/nitb_smpp/esme_ms_sms_storeforward.py
+++ b/sysmocom/suites/nitb_smpp/esme_ms_sms_storeforward.py
@@ -27,13 +27,13 @@
 esme.connect()
 nitb.subscriber_add(ms)
 
-wrong_msisdn = ms.msisdn + esme.msisdn
+wrong_msisdn = ms.msisdn() + esme.msisdn
 print('sending sms with wrong msisdn %s, it will fail' % wrong_msisdn)
 msg = Sms(esme.msisdn, wrong_msisdn, 'smpp message with wrong dest')
 esme.run_method_expect_failure(SMPP_ESME_RINVDSTADR, esme.sms_send_wait_resp, msg, esme.MSGMODE_STOREFORWARD)
 
 print('sending sms, it will be stored...')
-msg = Sms(esme.msisdn, ms.msisdn, 'smpp send not-yet-registered message')
+msg = Sms(esme.msisdn, ms.msisdn(), 'smpp send not-yet-registered message')
 umref = esme.sms_send_wait_resp(msg, esme.MSGMODE_STOREFORWARD, receipt=True)
 
 print('MS registers and will receive the SMS...')
@@ -45,7 +45,7 @@
 wait(esme.receipt_was_received, umref)
 
 print('checking MS can receive SMS while registered...')
-msg = Sms(esme.msisdn, ms.msisdn, 'smpp send already-registered message')
+msg = Sms(esme.msisdn, ms.msisdn(), 'smpp send already-registered message')
 umref = esme.sms_send_wait_resp(msg, esme.MSGMODE_STOREFORWARD, receipt=True)
 wait(ms.sms_was_received, msg)
 print('Waiting to receive and consume sms receipt with reference', umref)