diff --git a/gbproxy/GBProxy_Tests.ttcn b/gbproxy/GBProxy_Tests.ttcn
index 6141f6a..f1e8749 100644
--- a/gbproxy/GBProxy_Tests.ttcn
+++ b/gbproxy/GBProxy_Tests.ttcn
@@ -1,6 +1,7 @@
 module GBProxy_Tests {
 
 /* Osmocom GBProxy test suite in TTCN-3
+ * (C) 2020-2021 Harald Welte <laforge@osmocom.org>
  * (C) 2020 sysmocom - s.f.m.c. GmbH
  * All rights reserved.
  *
@@ -601,8 +602,8 @@
 type function void_fn(charstring id) runs on BSSGP_ConnHdlr;
 
 /* helper function to create, connect and start a BSSGP_ConnHdlr component */
-function f_start_handler(void_fn fn, charstring id, integer imsi_suffix,
-			 float t_guard := 30.0, integer sgsn_idx := 0, integer nri_idx := 0)
+function f_start_handler(void_fn fn, charstring id, integer imsi_suffix, float t_guard := 30.0,
+			 integer sgsn_idx := 0, integer nri_idx := 0, boolean have_ptmsi := true)
 runs on test_CT return BSSGP_ConnHdlr {
 	var BSSGP_ConnHdlr vc_conn;
 	var integer nri := mp_sgsn_nri[sgsn_idx][nri_idx];
@@ -622,6 +623,9 @@
 		sgsn_idx := sgsn_idx,
 		t_guard := t_guard
 	};
+	if (not have_ptmsi) {
+		pars.p_tmsi := omit;
+	}
 
 	vc_conn := BSSGP_ConnHdlr.create(id);
 
@@ -629,7 +633,8 @@
 	return vc_conn;
 }
 
-function f_start_handlers(void_fn fn, charstring id, integer imsi_suffix, float t_guard := 30.0)
+function f_start_handlers(void_fn fn, charstring id, integer imsi_suffix, float t_guard := 30.0,
+			  boolean have_ptmsi := true)
 runs on test_CT
 {
 	var integer sgsn_idx, nri_idx;
@@ -637,8 +642,8 @@
 		for (nri_idx := 0; nri_idx < lengthof(mp_sgsn_nri[sgsn_idx]); nri_idx:=nri_idx+1) {
 			var integer extd_imsi_suffix := 1000*sgsn_idx + 100*nri_idx;
 			var BSSGP_ConnHdlr vc_conn;
-			vc_conn := f_start_handler(fn, id, extd_imsi_suffix, t_guard,
-						   sgsn_idx, nri_idx);
+			vc_conn := f_start_handler(fn, id, extd_imsi_suffix, t_guard, sgsn_idx, nri_idx,
+						   have_ptmsi);
 			/* Idea: we could also run them in parallel ? */
 			vc_conn.done;
 		}