diff --git a/include/osmocom/gsm/lapdm.h b/include/osmocom/gsm/lapdm.h
index cc9c63f..adffbeb 100644
--- a/include/osmocom/gsm/lapdm.h
+++ b/include/osmocom/gsm/lapdm.h
@@ -127,7 +127,7 @@
 extern const char *lapdm_state_names[];
 
 /* initialize a LAPDm entity */
-void lapdm_entity_init(struct lapdm_entity *le, enum lapdm_mode mode);
+void lapdm_entity_init(struct lapdm_entity *le, enum lapdm_mode mode, int t200);
 void lapdm_channel_init(struct lapdm_channel *lc, enum lapdm_mode mode);
 
 /* deinitialize a LAPDm entity */