diff --git a/src/vlibapi/api.h b/src/vlibapi/api.h
index 3d5c869..431155c 100644
--- a/src/vlibapi/api.h
+++ b/src/vlibapi/api.h
@@ -109,6 +109,7 @@
 				      void *the_msg, vlib_main_t * vm,
 				      vlib_node_runtime_t * node,
 				      u8 is_private);
+u32 vl_msg_api_max_length (void *mp);
 vl_api_trace_t *vl_msg_api_trace_get (api_main_t * am,
 				      vl_api_trace_which_t which);
 void vl_msg_api_add_msg_name_crc (api_main_t * am, const char *string,