diff --git a/ospf6d/ospf6_message.h b/ospf6d/ospf6_message.h
index f8be627..186fc74 100644
--- a/ospf6d/ospf6_message.h
+++ b/ospf6d/ospf6_message.h
@@ -122,6 +122,7 @@
 void ospf6_lsupdate_print (struct ospf6_header *);
 void ospf6_lsack_print (struct ospf6_header *);
 
+int ospf6_iobuf_size (int size);
 int ospf6_receive (struct thread *thread);
 
 int ospf6_hello_send (struct thread *thread);