diff --git a/openbsc/include/openbsc/gb_proxy.h b/openbsc/include/openbsc/gb_proxy.h
index 3f81551..5a580cd 100644
--- a/openbsc/include/openbsc/gb_proxy.h
+++ b/openbsc/include/openbsc/gb_proxy.h
@@ -88,6 +88,8 @@
 	time_t timestamp;
 	uint8_t *mi_data;
 	size_t mi_data_len;
+
+	int enable_patching;
 };
 
 
diff --git a/openbsc/src/gprs/gb_proxy.c b/openbsc/src/gprs/gb_proxy.c
index 98b10b9..103ecb5 100644
--- a/openbsc/src/gprs/gb_proxy.c
+++ b/openbsc/src/gprs/gb_proxy.c
@@ -439,6 +439,9 @@
 	struct gbproxy_tlli_info *tlli_info;
 	struct gbproxy_patch_state *state = &peer->patch_state;
 
+	if (!is_mi_imsi(mi_data, mi_data_len))
+		return NULL;
+
 	llist_for_each_entry(tlli_info, &state->enabled_tllis, list) {
 		if (tlli_info->mi_data_len != mi_data_len)
 			continue;
@@ -600,6 +603,9 @@
 static void gbprox_update_tlli_info(struct gbproxy_tlli_info *tlli_info,
 				    const uint8_t *imsi, size_t imsi_len)
 {
+	if (!is_mi_imsi(imsi, imsi_len))
+		return;
+
 	tlli_info->mi_data_len = imsi_len;
 	tlli_info->mi_data =
 		talloc_realloc_size(tlli_info, tlli_info->mi_data, imsi_len);
@@ -607,26 +613,35 @@
 	memcpy(tlli_info->mi_data, imsi, imsi_len);
 }
 
+void gbprox_reassign_tlli(struct gbproxy_tlli_info *tlli_info,
+			  struct gbproxy_peer *peer, uint32_t new_tlli)
+{
+	if (new_tlli == tlli_info->tlli)
+		return;
+
+	LOGP(DGPRS, LOGL_INFO,
+	     "The TLLI has been reassigned from %08x to %08x\n",
+	     tlli_info->tlli, new_tlli);
+
+	/* TODO: Save old TLLI */
+	tlli_info->tlli = new_tlli;
+}
+
 void gbprox_register_tlli(struct gbproxy_peer *peer, uint32_t tlli,
 				 const uint8_t *imsi, size_t imsi_len)
 {
 	struct gbproxy_patch_state *state = &peer->patch_state;
 	struct gbproxy_tlli_info *tlli_info;
-	int enable_patching;
+	int enable_patching = -1;
 	time_t now = 0;
 	int tlli_already_known;
 
-	if (!imsi || (imsi[0] & GSM_MI_TYPE_MASK) != GSM_MI_TYPE_IMSI)
-		return;
-
-	if (!peer->cfg->check_imsi)
-		return;
-
 	/* Check, whether the IMSI matches */
-	enable_patching = gbprox_check_imsi(peer, imsi, imsi_len);
-
-	if (enable_patching < 0)
-		return;
+	if (is_mi_imsi(imsi, imsi_len)) {
+		enable_patching = gbprox_check_imsi(peer, imsi, imsi_len);
+		if (enable_patching < 0)
+			return;
+	}
 
 	tlli_info = gbprox_find_tlli(peer, tlli);
 
@@ -644,32 +659,23 @@
 
 	tlli_already_known = tlli_info != NULL;
 
-	if (!tlli_already_known && !enable_patching)
-		return;
-
 	tlli_info = gbprox_get_detached_tlli_info(peer, tlli_info, tlli);
 	OSMO_ASSERT(tlli_info != NULL);
 
-	if (enable_patching) {
-		if (!tlli_already_known)
-			LOGP(DGPRS, LOGL_INFO, "Adding TLLI %08x to list\n", tlli);
+	if (!tlli_already_known)
+		LOGP(DGPRS, LOGL_INFO, "Adding TLLI %08x to list\n", tlli);
 
-		now = time(NULL);
+	now = time(NULL);
 
-		gbprox_attach_tlli_info(peer, now, tlli_info);
-		gbprox_update_tlli_info(tlli_info, imsi, imsi_len);
+	gbprox_attach_tlli_info(peer, now, tlli_info);
+	gbprox_update_tlli_info(tlli_info, imsi, imsi_len);
+	if (enable_patching >= 0)
+		tlli_info->enable_patching = enable_patching;
 
-		gbprox_remove_stale_tllis(peer, now);
-		/* Be on the safe side, currently the new tlli_info won't be
-		 * removed, but this not enforced explicitely */
-		tlli_info = NULL;
-	} else {
-		LOGP(DGPRS, LOGL_INFO,
-		     "Removing TLLI %08x from list (patching no longer enabled)\n",
-		     tlli);
-		talloc_free(tlli_info);
-		tlli_info = NULL;
-	}
+	gbprox_remove_stale_tllis(peer, now);
+	/* Be on the safe side, currently the new tlli_info won't be
+	 * removed, but this not enforced explicitely */
+	tlli_info = NULL;
 
 	peer->ctrg->ctr[GBPROX_PEER_CTR_TLLI_CACHE_SIZE].current =
 		state->enabled_tllis_count;
@@ -694,11 +700,17 @@
 
 static int gbprox_check_tlli(struct gbproxy_peer *peer, uint32_t tlli)
 {
+	struct gbproxy_tlli_info *tlli_info;
+
 	LOGP(DGPRS, LOGL_INFO, "Checking TLLI %08x, class: %d\n",
 	     tlli, gprs_tlli_type(tlli));
 
-	return !peer->cfg->check_imsi ||
-		gbprox_find_tlli(peer, tlli) != NULL;
+	if (!peer->cfg->check_imsi)
+		return 1;
+
+	tlli_info = gbprox_find_tlli(peer, tlli);
+
+	return tlli_info != NULL && tlli_info->enable_patching;
 }
 
 /* check whether patching is enabled at this level */
@@ -1240,6 +1252,13 @@
 				struct gbproxy_parse_context *parse_ctx)
 {
 	const char *msg_name = "BSSGP";
+	struct gbproxy_tlli_info *tlli_info = NULL;
+
+	if (!peer->cfg->check_imsi)
+		return;
+
+	if (parse_ctx->tlli_enc)
+		tlli_info = gbprox_find_tlli(peer, parse_ctx->tlli);
 
 	if (parse_ctx->llc_msg_name)
 		msg_name = parse_ctx->llc_msg_name;
@@ -1290,7 +1309,8 @@
 		     msg_name, mi_buf);
 	}
 
-	if (parse_ctx->new_ptmsi_enc && parse_ctx->to_bss && parse_ctx->imsi) {
+	if (parse_ctx->tlli_enc && parse_ctx->new_ptmsi_enc &&
+	    parse_ctx->to_bss) {
 		/* A new PTMSI has been signaled in the message,
 		 * register new TLLI */
 		uint32_t new_ptmsi;
@@ -1306,9 +1326,11 @@
 		LOGP(DGPRS, LOGL_INFO,
 		     "Got new TLLI/PTMSI %08x/%08x (current is %08x)\n",
 		     new_tlli, new_ptmsi, parse_ctx->tlli);
-		gbprox_register_tlli(peer, new_ptmsi,
+		if (tlli_info)
+			gbprox_reassign_tlli(tlli_info, peer, new_tlli);
+		gbprox_register_tlli(peer, new_tlli,
 				     parse_ctx->imsi, parse_ctx->imsi_len);
-	} else if (parse_ctx->tlli && parse_ctx->imsi) {
+	} else if (parse_ctx->tlli_enc && parse_ctx->llc) {
 		gbprox_register_tlli(peer, parse_ctx->tlli,
 				     parse_ctx->imsi, parse_ctx->imsi_len);
 	}
diff --git a/openbsc/src/gprs/gb_proxy_vty.c b/openbsc/src/gprs/gb_proxy_vty.c
index 68d5e74..ec73ae6 100644
--- a/openbsc/src/gprs/gb_proxy_vty.c
+++ b/openbsc/src/gprs/gb_proxy_vty.c
@@ -368,10 +368,14 @@
 
 		llist_for_each_entry(tlli_info, &state->enabled_tllis, list) {
 			time_t age = now - tlli_info->timestamp;
-			snprintf(mi_buf, sizeof(mi_buf), "(invalid)");
-			gsm48_mi_to_string(mi_buf, sizeof(mi_buf),
-					   tlli_info->mi_data,
-					   tlli_info->mi_data_len);
+			if (tlli_info->mi_data_len > 0) {
+				snprintf(mi_buf, sizeof(mi_buf), "(invalid)");
+				gsm48_mi_to_string(mi_buf, sizeof(mi_buf),
+						   tlli_info->mi_data,
+						   tlli_info->mi_data_len);
+			} else {
+				snprintf(mi_buf, sizeof(mi_buf), "(none)");
+			}
 			vty_out(vty, "  TLLI %08x, IMSI %s, AGE %d%s",
 				tlli_info->tlli, mi_buf, (int)age,
 				VTY_NEWLINE);
diff --git a/openbsc/tests/gbproxy/gbproxy_test.c b/openbsc/tests/gbproxy/gbproxy_test.c
index 769dc67..229d2d4 100644
--- a/openbsc/tests/gbproxy/gbproxy_test.c
+++ b/openbsc/tests/gbproxy/gbproxy_test.c
@@ -116,10 +116,14 @@
 		llist_for_each_entry(tlli_info, &state->enabled_tllis, list) {
 			char mi_buf[200];
 			time_t age = now - tlli_info->timestamp;
-			snprintf(mi_buf, sizeof(mi_buf), "(invalid)");
-			gsm48_mi_to_string(mi_buf, sizeof(mi_buf),
-					   tlli_info->mi_data,
-					   tlli_info->mi_data_len);
+			if (tlli_info->mi_data_len > 0) {
+				snprintf(mi_buf, sizeof(mi_buf), "(invalid)");
+				gsm48_mi_to_string(mi_buf, sizeof(mi_buf),
+						   tlli_info->mi_data,
+						   tlli_info->mi_data_len);
+			} else {
+				snprintf(mi_buf, sizeof(mi_buf), "(none)");
+			}
 			rc = fprintf(stream,
 				     "%*s      TLLI %08x, IMSI %s, AGE %d\n",
 				     indent, "",
diff --git a/openbsc/tests/gbproxy/gbproxy_test.ok b/openbsc/tests/gbproxy/gbproxy_test.ok
index ee67c33..4553648 100644
--- a/openbsc/tests/gbproxy/gbproxy_test.ok
+++ b/openbsc/tests/gbproxy/gbproxy_test.ok
@@ -1807,8 +1807,9 @@
     RAID patched              (SGSN): 3
     APN patched                     : 3
     Attach Request count            : 1
-    TLLI cache size                 : 1
-    TLLI-Cache: 1
+    TLLI cache size                 : 2
+    TLLI-Cache: 2
+      TLLI efe2b700, IMSI (none), AGE 0
       TLLI efe28117, IMSI 12131415161718, AGE 0
 PROCESSING DETACH REQ from 0x01020304:1111
 00 00 10 02 01 ef e2 b7 00 00 00 04 08 88 11 22 33 40 50 60 75 30 00 80 0e 00 15 01 c0 19 08 05 01 18 05 f4 ef e2 b7 00 19 03 b9 97 cb 7e e1 41 
@@ -1841,7 +1842,9 @@
     RAID patched              (SGSN): 3
     APN patched                     : 3
     Attach Request count            : 1
-    TLLI-Cache: 0
+    TLLI cache size                 : 1
+    TLLI-Cache: 1
+      TLLI efe28117, IMSI 12131415161718, AGE 0
 --- Bad cases ---
 
 TLLI is already detached, shouldn't patch
@@ -1879,7 +1882,10 @@
     RAID patched              (SGSN): 3
     APN patched                     : 3
     Attach Request count            : 1
-    TLLI-Cache: 0
+    TLLI cache size                 : 2
+    TLLI-Cache: 2
+      TLLI efe2b700, IMSI (none), AGE 0
+      TLLI efe28117, IMSI 12131415161718, AGE 0
 Test TLLI info expiry
 
 Test TLLI replacement: