diff --git a/include/osmocom/gsm/protocol/gsm_04_08.h b/include/osmocom/gsm/protocol/gsm_04_08.h
index 3ad7dfd..39470e7 100644
--- a/include/osmocom/gsm/protocol/gsm_04_08.h
+++ b/include/osmocom/gsm/protocol/gsm_04_08.h
@@ -1257,6 +1257,9 @@
 	uint8_t rac;		/* Routing Area Code */
 } __attribute__ ((packed));
 
+#define GSM48_CELL_CHAN_DESC_SIZE	16
 
+#define GSM_MACBLOCK_LEN	23
+#define GSM_MACBLOCK_PADDING	0x2b
 
 #endif /* PROTO_GSM_04_08_H */