diff --git a/openbsc/tests/gbproxy/gbproxy_test.c b/openbsc/tests/gbproxy/gbproxy_test.c
index 75dc173..a0c202a 100644
--- a/openbsc/tests/gbproxy/gbproxy_test.c
+++ b/openbsc/tests/gbproxy/gbproxy_test.c
@@ -124,6 +124,29 @@
 	0x00, 0x5a, 0xff, 0x02
 };
 
+/* Base Station Subsystem GPRS Protocol: GSM A-I/F DTAP - Detach Request */
+static const unsigned char bssgp_detach_req[44] = {
+	0x01, 0xef, 0xe2, 0xb7, 0x00, 0x00, 0x00, 0x04,
+	0x08, 0x88, 0x11, 0x22, 0x33, 0x40, 0x50, 0x60,
+	0x75, 0x30, 0x00, 0x80, 0x0e, 0x00, 0x15, 0x01,
+	0xc0, 0x19, 0x08, 0x05, 0x01, 0x18, 0x05, 0xf4,
+	0xef, 0xe2, 0xb7, 0x00, 0x19, 0x03, 0xb9, 0x97,
+	0xcb, 0x7e, 0xe1, 0x41
+};
+
+/* Base Station Subsystem GPRS Protocol: GSM A-I/F DTAP - Detach Accept */
+static const unsigned char bssgp_detach_acc[67] = {
+	0x00, 0xef, 0xe2, 0xb7, 0x00, 0x00, 0x50, 0x20,
+	0x16, 0x82, 0x02, 0x58, 0x13, 0x99, 0x18, 0xb3,
+	0x43, 0x2b, 0x25, 0x96, 0x62, 0x00, 0x60, 0x80,
+	0x9a, 0xc2, 0xc6, 0x62, 0x00, 0x60, 0x80, 0xba,
+	0xc8, 0xc6, 0x62, 0x00, 0x60, 0x80, 0x00, 0x0a,
+	0x82, 0x08, 0x02, 0x0d, 0x88, 0x11, 0x12, 0x13,
+	0x14, 0x15, 0x16, 0x17, 0x18, 0x00, 0x81, 0x00,
+	0x0e, 0x89, 0x41, 0xc0, 0x15, 0x08, 0x06, 0x00,
+	0xf7, 0x35, 0xf0
+};
+
 static int gprs_process_message(struct gprs_ns_inst *nsi, const char *text,
 				struct sockaddr_in *peer, const unsigned char* data,
 				size_t data_len);
@@ -882,11 +905,22 @@
 			 &bss_peer[0], 0x1002,
 			 bssgp_act_pdp_ctx_req, sizeof(bssgp_act_pdp_ctx_req));
 
+	/* Detach */
+	send_ns_unitdata(nsi, "DETACH REQ", &bss_peer[0], 0x1002,
+			 bssgp_detach_req, sizeof(bssgp_detach_req));
+
+	send_ns_unitdata(nsi, "DETACH ACC", &sgsn_peer, 0x1002,
+			 bssgp_detach_acc, sizeof(bssgp_detach_acc));
+
 	gbprox_dump_global(stdout, 0);
 	gbprox_dump_peers(stdout, 0);
 
 	printf("--- Bad cases ---\n\n");
 
+	printf("TLLI is already detached, shouldn't patch (expected failure)\n");
+	send_ns_unitdata(nsi, "ACT PDP CTX REQ", &bss_peer[0], 0x1002,
+			 bssgp_act_pdp_ctx_req, sizeof(bssgp_act_pdp_ctx_req));
+
 	send_bssgp_reset_ack(nsi, &sgsn_peer, 0x1eee);
 	send_bssgp_suspend_ack(nsi, &sgsn_peer, &rai_unknown);