diff --git a/msc/BSC_ConnectionHandler.ttcn b/msc/BSC_ConnectionHandler.ttcn
index 3fa5fac..cf4e846 100644
--- a/msc/BSC_ConnectionHandler.ttcn
+++ b/msc/BSC_ConnectionHandler.ttcn
@@ -93,6 +93,9 @@
 	BSSMAP_IE_ClassmarkInformationType2 cm2,
 	BSSMAP_IE_ClassmarkInformationType3 cm3 optional,
 	AuthVector vec optional,
+	/* BSC_ConnectionHandler generates an auth vector in as_GSUP_SAI(). For tests that want control over which
+	 * vector is used, pass vec_keep := true to not regenerate a new auth vector in as_GSUP_SAI(). */
+	boolean vec_keep,
 	BSC_ConnHdlrNetworkPars net,
 	boolean send_early_cm,
 	charstring ipa_ctrl_ip,
@@ -426,7 +429,9 @@
 var GSUP_IE auth_tuple;
 [] GSUP.receive(tr_GSUP_SAI_REQ(g_pars.imsi)) {
 	if (g_pars.use_umts_aka) {
-		g_pars.vec := f_gen_auth_vec_3g();
+		if (not g_pars.vec_keep) {
+			g_pars.vec := f_gen_auth_vec_3g();
+		}
 		auth_tuple := valueof(ts_GSUP_IE_AuthTuple2G3G(g_pars.vec.rand,
 								g_pars.vec.sres,
 								g_pars.vec.kc,
@@ -436,7 +441,9 @@
 								g_pars.vec.res));
 		GSUP.send(ts_GSUP_SAI_RES(g_pars.imsi, auth_tuple));
 	} else {
-		g_pars.vec := f_gen_auth_vec_2g();
+		if (not g_pars.vec_keep) {
+			g_pars.vec := f_gen_auth_vec_2g();
+		}
 		auth_tuple := valueof(ts_GSUP_IE_AuthTuple2G(g_pars.vec.rand,
 								g_pars.vec.sres,
 								g_pars.vec.kc));