diff --git a/msc/BSC_ConnectionHandler.ttcn b/msc/BSC_ConnectionHandler.ttcn
index 072f38d..658923e 100644
--- a/msc/BSC_ConnectionHandler.ttcn
+++ b/msc/BSC_ConnectionHandler.ttcn
@@ -833,9 +833,15 @@
 	}
 }
 
-function f_perform_lu()
+function f_perform_lu(template (omit) MobileIdentityLV use_mi := omit)
 runs on BSC_ConnHdlr {
-	var PDU_ML3_MS_NW l3_lu := f_build_lu_imsi(g_pars.imsi)
+	var MobileIdentityLV mi;
+	if (istemplatekind(use_mi, "omit")) {
+		mi := valueof(ts_MI_IMSI_LV(g_pars.imsi));
+	} else {
+		mi := valueof(use_mi);
+	}
+	var PDU_ML3_MS_NW l3_lu := f_build_lu(mi);
 	var PDU_DTAP_MT dtap_mt;
 
 	/* tell GSUP dispatcher to send this IMSI to us */