diff --git a/include/osmocom/gsm/lapdm.h b/include/osmocom/gsm/lapdm.h
index 42ebbce..6812102 100644
--- a/include/osmocom/gsm/lapdm.h
+++ b/include/osmocom/gsm/lapdm.h
@@ -51,6 +51,7 @@
 #define LAPDM_ENT_F_EMPTY_FRAME		0x0001
 #define LAPDM_ENT_F_POLLING_ONLY	0x0002
 #define LAPDM_ENT_F_DROP_2ND_REJ	0x0004
+#define LAPDM_ENT_F_RTS			0x0008
 
 /*! a LAPDm Entity */
 struct lapdm_entity {