diff --git a/include/osmocom/abis/e1_input.h b/include/osmocom/abis/e1_input.h
index acbc110..9825999 100644
--- a/include/osmocom/abis/e1_input.h
+++ b/include/osmocom/abis/e1_input.h
@@ -151,6 +151,7 @@
 	S_INP_NONE,
 	S_INP_TEI_UP,
 	S_INP_TEI_DN,
+	S_INP_TEI_UNKNOWN,
 	S_INP_LINE_INIT,
 	S_INP_LINE_ALARM,
 	S_INP_LINE_NOALARM,
diff --git a/include/osmocom/abis/lapd.h b/include/osmocom/abis/lapd.h
index fb980d1..dd22028 100644
--- a/include/osmocom/abis/lapd.h
+++ b/include/osmocom/abis/lapd.h
@@ -26,8 +26,20 @@
 	struct llist_head tei_list;	/* list of TEI in this LAPD instance */
 };
 
-extern uint8_t *lapd_receive(struct lapd_instance *li, uint8_t *data, unsigned int len,
-			     int *ilen, lapd_mph_type *prim);
+enum lapd_recv_errors {
+	LAPD_ERR_NONE = 0,
+	LAPD_ERR_BAD_LEN,
+	LAPD_ERR_BAD_ADDR,
+	LAPD_ERR_UNKNOWN_S_CMD,
+	LAPD_ERR_UNKNOWN_U_CMD,
+	LAPD_ERR_UNKNOWN_TEI,
+	LAPD_ERR_BAD_CMD,
+	__LAPD_ERR_MAX
+};
+
+extern uint8_t *lapd_receive(struct lapd_instance *li, uint8_t *data,
+			     unsigned int len, int *ilen, lapd_mph_type *prim,
+			     int *error);
 
 extern void lapd_transmit(struct lapd_instance *li, uint8_t tei, uint8_t sapi,
 			  uint8_t *data, unsigned int len);