diff --git a/tests/msc_vlr/msc_vlr_test_reject_concurrency.c b/tests/msc_vlr/msc_vlr_test_reject_concurrency.c
new file mode 100644
index 0000000..1598858
--- /dev/null
+++ b/tests/msc_vlr/msc_vlr_test_reject_concurrency.c
@@ -0,0 +1,379 @@
+/* Osmocom MSC+VLR end-to-end tests */
+
+/* (C) 2017 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * Author: Neels Hofmeyr <nhofmeyr@sysmocom.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "msc_vlr_tests.h"
+
+void test_reject_2nd_conn()
+{
+	struct gsm_subscriber_connection *conn1;
+	comment_start();
+
+	btw("Location Update Request on one connection");
+	lu_result_sent = RES_NONE;
+	gsup_expect_tx("04010809710000004026f0");
+	ms_sends_msg("050802008168000130089910070000006402");
+	OSMO_ASSERT(gsup_tx_confirmed);
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+	EXPECT_CONN_COUNT(1);
+
+	btw("Another Location Update Request from the same subscriber on another connection is rejected");
+	conn1 = g_conn;
+	g_conn = NULL;
+	ms_sends_msg("050802008168000130089910070000006402");
+	VERBOSE_ASSERT(lu_result_sent, == RES_REJECT, "%d");
+	EXPECT_CONN_COUNT(1);
+
+
+	BTW("The first connection can still complete its LU");
+	btw("HLR sends _INSERT_DATA_REQUEST, VLR responds with _INSERT_DATA_RESULT");
+	g_conn = conn1;
+	lu_result_sent = RES_NONE;
+	gsup_rx("10010809710000004026f00804036470f1",
+		"12010809710000004026f0");
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+
+	btw("HLR also sends GSUP _UPDATE_LOCATION_RESULT");
+	gsup_rx("06010809710000004026f0", NULL);
+
+	btw("LU was successful, and the conn has already been closed");
+	VERBOSE_ASSERT(lu_result_sent, == RES_ACCEPT, "%d");
+	EXPECT_CONN_COUNT(0);
+
+	clear_vlr();
+	comment_end();
+}
+
+void _normal_lu_part1()
+{
+	btw("Location Update Request");
+	lu_result_sent = RES_NONE;
+	gsup_expect_tx("04010809710000004026f0");
+	ms_sends_msg("050802008168000130089910070000006402");
+	OSMO_ASSERT(gsup_tx_confirmed);
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+	EXPECT_CONN_COUNT(1);
+}
+
+void _normal_lu_part2()
+{
+	btw("HLR sends _INSERT_DATA_REQUEST, VLR responds with _INSERT_DATA_RESULT");
+	lu_result_sent = RES_NONE;
+	gsup_rx("10010809710000004026f00804036470f1",
+		"12010809710000004026f0");
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+
+	btw("HLR also sends GSUP _UPDATE_LOCATION_RESULT");
+	gsup_rx("06010809710000004026f0", NULL);
+
+	btw("LU was successful, and the conn has already been closed");
+	VERBOSE_ASSERT(lu_result_sent, == RES_ACCEPT, "%d");
+	EXPECT_CONN_COUNT(0);
+}
+
+void _normal_lu()
+{
+	BTW("Subscriber does a normal LU");
+	_normal_lu_part1();
+	_normal_lu_part2();
+}
+
+void _normal_cm_service_req()
+{
+	BTW("Subscriber does a normal CM Service Request");
+	cm_service_result_sent = RES_NONE;
+	ms_sends_msg("05247803305886089910070000006402");
+	OSMO_ASSERT(g_conn);
+	OSMO_ASSERT(g_conn->conn_fsm);
+	OSMO_ASSERT(g_conn->vsub);
+	VERBOSE_ASSERT(cm_service_result_sent, == RES_ACCEPT, "%d");
+	EXPECT_ACCEPTED(true);
+}
+
+void _page()
+{
+	const char *imsi = "901700000004620";
+	struct vlr_subscr *vsub;
+
+	BTW("an SMS is sent, MS is paged");
+	paging_expect_imsi(imsi);
+	paging_sent = false;
+	vsub = vlr_subscr_find_by_imsi(net->vlr, imsi);
+	OSMO_ASSERT(vsub);
+	VERBOSE_ASSERT(llist_count(&vsub->cs.requests), == 0, "%d");
+
+	send_sms(vsub, vsub,
+		 "Privacy in residential applications is a desirable"
+		 " marketing option.");
+
+	VERBOSE_ASSERT(llist_count(&vsub->cs.requests), == 1, "%d");
+	vlr_subscr_put(vsub);
+	vsub = NULL;
+	VERBOSE_ASSERT(paging_sent, == true, "%d");
+	VERBOSE_ASSERT(paging_stopped, == false, "%d");
+}
+
+void _paging_resp_part1()
+{
+	btw("MS replies with Paging Response, we deliver the SMS");
+	dtap_expect_tx("09" /* SMS messages */
+		       "01" /* CP-DATA */
+		       "58" /* length */
+		       "01" /* Network to MS */
+		       "00" /* reference */
+		       /* originator (gsm411_send_sms() hardcodes this weird nr) */
+		       "0791" "447758100650" /* 447785016005 */
+		       "00" /* dest */
+		       /* SMS TPDU */
+		       "4c" /* len */
+		       "00" /* SMS deliver */
+		       "05806470f1" /* originating address 46071 */
+		       "00" /* TP-PID */
+		       "00" /* GSM default alphabet */
+		       "071010" /* Y-M-D (from wrapped gsm340_gen_scts())*/
+		       "000000" /* H-M-S */
+		       "00" /* GMT+0 */
+		       "44" /* data length */
+		       "5079da1e1ee7416937485e9ea7c965373d1d6683c270383b3d0e"
+		       "d3d36ff71c949e83c22072799e9687c5ec32a81d96afcbf4b4fb"
+		       "0c7ac3e9e9b7db05");
+	ms_sends_msg("06270703305882089910070000006402");
+	VERBOSE_ASSERT(dtap_tx_confirmed, == true, "%d");
+	VERBOSE_ASSERT(paging_stopped, == true, "%d");
+
+	btw("conn is still open to wait for SMS ack dance");
+	EXPECT_CONN_COUNT(1);
+}
+
+void _paging_resp_part2(int expect_conn_count)
+{
+	btw("MS replies with CP-ACK for received SMS");
+	ms_sends_msg("8904");
+	EXPECT_CONN_COUNT(1);
+
+	btw("MS also sends RP-ACK, MSC in turn sends CP-ACK for that");
+	dtap_expect_tx("0904");
+	ms_sends_msg("890106020041020000");
+	VERBOSE_ASSERT(dtap_tx_confirmed, == true, "%d");
+
+	btw("SMS is done");
+	EXPECT_CONN_COUNT(expect_conn_count);
+}
+
+void test_reject_lu_during_lu()
+{
+	comment_start();
+
+	_normal_lu_part1();
+
+	BTW("Another Location Update Request from the same subscriber on the same conn is dropped silently");
+	ms_sends_msg("050802008168000130089910070000006402");
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+	EXPECT_CONN_COUNT(1);
+
+	BTW("The first LU can still complete");
+	_normal_lu_part2();
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_cm_during_lu()
+{
+	comment_start();
+
+	_normal_lu_part1();
+
+	BTW("A CM Service Request in the middle of a LU is rejected");
+	cm_service_result_sent = RES_NONE;
+	dtap_expect_tx("052211");
+	ms_sends_msg("05247803305886089910070000006402");
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+	VERBOSE_ASSERT(cm_service_result_sent, == RES_NONE, "%d");
+	EXPECT_CONN_COUNT(1);
+
+	BTW("The first LU can still complete");
+	_normal_lu_part2();
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_paging_resp_during_lu()
+{
+	comment_start();
+
+	_normal_lu_part1();
+
+	BTW("An erratic Paging Response is dropped silently");
+	ms_sends_msg("06270703305882089910070000006402");
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+	EXPECT_CONN_COUNT(1);
+
+	BTW("The first LU can still complete");
+	_normal_lu_part2();
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_lu_during_cm()
+{
+	comment_start();
+
+	_normal_lu();
+	_normal_cm_service_req();
+
+	btw("A LU request on an open conn is dropped silently");
+	/* TODO: accept periodic LU on an already open conn? */
+	lu_result_sent = RES_NONE;
+	ms_sends_msg("050802008168000130089910070000006402");
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+	EXPECT_CONN_COUNT(1);
+
+	BTW("subscriber detaches");
+	ms_sends_msg("050130089910070000006402");
+	EXPECT_CONN_COUNT(0);
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_cm_during_cm()
+{
+	comment_start();
+
+	_normal_lu();
+	_normal_cm_service_req();
+
+	btw("A second CM Service Request on the same conn is accepted without another auth dance");
+	cm_service_result_sent = RES_NONE;
+	ms_sends_msg("05247803305886089910070000006402");
+	VERBOSE_ASSERT(cm_service_result_sent, == RES_ACCEPT, "%d");
+	EXPECT_CONN_COUNT(1);
+
+	BTW("subscriber detaches");
+	ms_sends_msg("050130089910070000006402");
+	EXPECT_CONN_COUNT(0);
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_paging_resp_during_cm()
+{
+	comment_start();
+
+	_normal_lu();
+	_normal_cm_service_req();
+
+	BTW("An erratic Paging Response on the same conn is dropped silently");
+	ms_sends_msg("06270703305882089910070000006402");
+	EXPECT_CONN_COUNT(1);
+
+	BTW("The original CM Service Request can conclude");
+	btw("a USSD request is serviced");
+	dtap_expect_tx_ussd("Your extension is 46071\r");
+	ms_sends_msg("0b3b1c15a11302010002013b300b04010f0406aa510c061b017f0100");
+
+	btw("all requests serviced, conn has been released");
+	EXPECT_CONN_COUNT(0);
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_paging_resp_during_paging_resp()
+{
+	comment_start();
+
+	_normal_lu();
+	_page();
+	_paging_resp_part1();
+
+	BTW("MS sends another erratic Paging Response which is dropped silently");
+	ms_sends_msg("06270703305882089910070000006402");
+
+	_paging_resp_part2(0);
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_lu_during_paging_resp()
+{
+	comment_start();
+
+	_normal_lu();
+	_page();
+	_paging_resp_part1();
+
+	BTW("MS sends erratic LU Request, which is dropped silently");
+	lu_result_sent = RES_NONE;
+	ms_sends_msg("050802008168000130089910070000006402");
+	VERBOSE_ASSERT(lu_result_sent, == RES_NONE, "%d");
+	EXPECT_CONN_COUNT(1);
+
+	_paging_resp_part2(0);
+
+	clear_vlr();
+	comment_end();
+}
+
+void test_reject_cm_during_paging_resp()
+{
+	comment_start();
+
+	_normal_lu();
+	_page();
+	_paging_resp_part1();
+
+	BTW("CM Service Request during open connection is accepted");
+	cm_service_result_sent = RES_NONE;
+	ms_sends_msg("05247803305886089910070000006402");
+	VERBOSE_ASSERT(cm_service_result_sent, == RES_ACCEPT, "%d");
+	EXPECT_CONN_COUNT(1);
+	VERBOSE_ASSERT(g_conn->received_cm_service_request, == true, "%d");
+
+	_paging_resp_part2(1);
+
+	BTW("subscriber detaches");
+	ms_sends_msg("050130089910070000006402");
+	EXPECT_CONN_COUNT(0);
+
+	clear_vlr();
+	comment_end();
+}
+
+msc_vlr_test_func_t msc_vlr_tests[] = {
+	test_reject_2nd_conn,
+	test_reject_lu_during_lu,
+	test_reject_cm_during_lu,
+	test_reject_paging_resp_during_lu,
+	test_reject_lu_during_cm,
+	test_reject_cm_during_cm,
+	test_reject_paging_resp_during_cm,
+	test_reject_lu_during_paging_resp,
+	test_reject_cm_during_paging_resp,
+	test_reject_paging_resp_during_paging_resp,
+	NULL
+};