diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn
index 7d9c098..9a37fb0 100644
--- a/msc/MSC_Tests.ttcn
+++ b/msc/MSC_Tests.ttcn
@@ -652,6 +652,20 @@
 	vc_conn.done;
 }
 
+private function f_tc_lu_imsi_auth3g_tmsi(charstring id, BSC_ConnHdlrPars pars) runs on BSC_ConnHdlr {
+	pars.net.expect_auth := true;
+	pars.use_umts_aka := true;
+	f_init_handler(pars);
+	f_perform_lu();
+}
+testcase TC_lu_imsi_auth3g_tmsi() runs on MTC_CT {
+	var BSC_ConnHdlr vc_conn;
+	f_init();
+	f_vty_config(MSCVTY, "network", "authentication required");
+
+	vc_conn := f_start_handler(refers(f_tc_lu_imsi_auth3g_tmsi), 1005);
+	vc_conn.done;
+}
 
 /* Send CM SERVICE REQ for IMSI that has never performed LU before */
 private function f_tc_cmserv_imsi_unknown(charstring id, BSC_ConnHdlrPars pars)
@@ -4667,6 +4681,7 @@
 	execute( TC_lu_imsi_reject() );
 	execute( TC_lu_imsi_timeout_gsup() );
 	execute( TC_lu_imsi_auth_tmsi() );
+	execute( TC_lu_imsi_auth3g_tmsi() );
 	execute( TC_cmserv_imsi_unknown() );
 	execute( TC_lu_and_mo_call() );
 	execute( TC_lu_auth_sai_timeout() );