diff --git a/msc/MSC_Tests.ttcn b/msc/MSC_Tests.ttcn
index dc5303e..dc3ad1e 100644
--- a/msc/MSC_Tests.ttcn
+++ b/msc/MSC_Tests.ttcn
@@ -807,6 +807,8 @@
 
 /* Test LU by TMSI with unknown TMSI, expect (and answer) ID REQ. */
 private function f_tc_lu_tmsi_noauth_unknown(charstring id, BSC_ConnHdlrPars pars) runs on BSC_ConnHdlr {
+	/* We piggyback a test for an MSC crash on overlong IMSI (OS#2864) onto this test. */
+	var hexstring overlong_imsi := '012345789ABCDEF0123456789ABCDEF'H;
 	f_init_handler(pars);
 
 	var PDU_ML3_MS_NW l3_lu := f_build_lu_tmsi('01020304'O); /* FIXME: Random */
@@ -823,6 +825,7 @@
 
 	/* Wait for + respond to ID REQ (IMSI) */
 	BSSAP.receive(tr_PDU_DTAP_MT(tr_ML3_MT_MM_ID_Req('001'B)));
+	BSSAP.send(ts_PDU_DTAP_MO(ts_ML3_MO_MM_ID_Rsp_IMSI(overlong_imsi))); /* test for OS#2864 */
 	BSSAP.send(ts_PDU_DTAP_MO(ts_ML3_MO_MM_ID_Rsp_IMSI(g_pars.imsi)));
 
 	/* Expect MSC to do UpdateLocation to HLR; respond to it */